[cctalk] Re: Thirties techies and computing history
On Sun, May 19, 2024 at 4:56 PM Tarek Hoteit via cctalk wrote: > > Thank you, Josh. How did your passion start with classical computers? Maybe > this helps in understanding the generation? I know how I got started, but not really why. Although I can explain how it progressed. It was May 1986, I was at a sale of old electronics hoping to get a keyboard for my homebrew computer (this was before cheap PC keyboards in the UK). I saw a Philips P850 minicomputer being sold essentially for the scrap metal price. It had the user and service manuals with it, and it had a lights-and-switches front panel which I'd read about and never used. I bought it and somehow got it back to my student room. That evening I realised that there was a period of about 25 years of computing which was going to be lost and forgotten if nobody did something about it. So I did something and started collecting and restoring all the old computers I could find. It was a lot easier to find minicomputers and the like back then than it is now. But why did I buy that initial P850? I am not sure. I've always been interested in the history of electronics and computers, so perhaps that was it. -tony
[cctalk] Re: NTSC TV demodulator
On Sun, May 19, 2024 at 1:08 PM Will Cooke via cctalk wrote: > Does anyone know of a small TV tuner that tunes old analog TV channels (US > NTSC) and outputs composite or VGA or HDMI signals? I've looked around a bit > but haven't found anything. It's relatively easy to build one, but I would > prefer a pre-built solution. And I'm sure others have run into this same > problem. Not for NTSC video, but for the UK UHF analogue TV... About 30 years ago we had a hobbyist electronics shop chain called Maplin, who produced and sold their own range of kits, many of them very good. When NICAM stereo TV sound was introduced in the UK, they produced a kit to decode the NICAM signal to audio. In fact it was a total of 3 kits -- the NICAM decoder board, a TV tuner/IF strip to feed it (if you didn't want to try to tap off the NICAM subcarrier from your existing TV 's tuner), and the case/connectors/tuner channel memory/etc.. I built the entire system for my parents who had a VCR [1] that could record stereo sound from line-level inputs but which pre-dated NICAM. I then realised that the tuner/IF board on its own, with a multi-turn pot added for tuning (rather than the remote control/memory control IC used in the full unit) would be ideal for turning the RF output of UK home computers into composite video. So I built a second tuner board for that. Still have it, still use it. -tony
[cctalk] Re: DOS p-System Pascal: (Was: Saga of CP/M)
On Thu, May 9, 2024 at 1:08 PM Bill Degnan via cctalk wrote: > > I meant UCSD not native Pascal. I assume the SAGE was popular with those > who bought them, but relative to the PC, quite obscure of a computer. Most > people today have little knowledge of the SAGE II / IV. How many even > exist today? A hundred? A trivial data point, but a Sage II along with a somewhat-related Stride 440 (68020 CPU running the P-system) exist in my collection. -tony
[cctalk] Re: APL (Was: BASIC
On Wed, May 8, 2024 at 3:25 PM Harald Arnesen via cctalk wrote: > > Paul Koning via cctalk [07/05/2024 19.31]: > > > (Then again, I had a classmate who was taking a double major: math and > > music composition...) > > Mathemathics and music is not a rare combination - see Tom Lehrer, for > instance. I am, of course, thinking of the well-known book 'Godel, Escher and Bach, an Eternal Golden Braid' -tony
[cctalk] Re: FWIW CD & DVD demagnitizitation [was: Double Density 3.5" Floppy Disks]
On Wed, May 8, 2024 at 12:51 AM Chuck Guzis via cctalk wrote: > > On 5/7/24 15:21, Fred Cisin via cctalk wrote: > > How difficult is it to measure and compare "With/Without" signals? > > > > If you peruse the old Bob Pease articles on "Electronic Design" > magazine, I believe more than once, he alluded to a proposed "blind > test"--two boxes; one filled with the latest audiophilatic super speaker > cable and the other with standard lamp cord with splices. > > I don't believe that anyone took him up on the proposed challenge. There is a UK audio manufacturer which produces equipment under the name 'QUAD'. Their products are based on electronic engineering, not magic, They make amplifiers and also one of the few full-range electrostatic loudspeaker units. Anyway, some of their engineers were setting up for an exhibition/demonstration when they realised they'd forgotten to bring any speaker cable. No problem, one of them goes to the local 'DIY Shed' (large hardware store) and buys some normal mains cable[1]. They use this and not surprisingly it sounds great. [1] Apparently there's a slogan on the wall of the QUAD workshop 'Ohm's Law rules here. Oxygen-free cable is not required' Next day, said chain of 'DIY sheds' gets a run on that mains cable. Audiophools were buying this magic speaker cable -tony
[cctalk] Re: Double Density 3.5" Floppy Disks
On Wed, May 1, 2024 at 5:38 AM Paul Berger via cctalk wrote: > > As Mike said there are two models 9114A and 9114B, they are functionally > equivalent, however the B model uses a 1/2 high drive mechanism and I > believe there are changes to the controller as well, but I have only > seen the inside of a B model. I've got both types and not surprisingly have been inside them. The controllers are similar in design -- the main changes are for the different drive type and the better battery status monitor on the 'B' -- but are not interchangeable. You probably could get it to work, but.. The -A uses the original Sony 3.5" double-head drive. This always runs at 600rpm, the HP one is not modified. The -B uses a later drive, also 600rpm, which shares a lot of parts with the Apple 800K drive (head carriage, stepper motor, analogue IC...) should you need to do repairs. The older drive has a 26 pin data cable and separate 4 pin power cable, the later drive has a 34 pin cable for data and power (power is on some of the odd-numbered pin, they are not all grounds as you might expect). The disk-inserted sensor on the -A is a spring-loaded plastic part which interrupts the beam of a slotted optoswitch on the motor PCB when a disk is present. Amazingly it lines up with the 'high desity hole' in 1.4M disks. So unless you rigidly block that hole it is likely the drive will not detect such a disk. As others have said the 1.4M disks are higher coercivity so using them is unreliable at best. -tony
[cctalk] Versatec Electrostatic Printers (was :Re: Re: Odd IBM mass storage systems)
On Sat, Apr 13, 2024 at 10:48 PM Jon Elson via cctalk wrote: > Yes, there were a number of Versatec models for different > paper sizes and pixel density. Does anyone else have one in their collection? I have an ICL-badged V80 which has a GPIB interface to link it to a PERQ. I also have the schematics, etc for the plain V80 but nothing on the GPIB interface (ether user or service data). IIRC the V80 is based round a Texas 16-bit microprocessor with some AM2900-series sequencers and ROMs to control the electrode timing. As Jon said in the bit I deleted, there's a 'nib electrode' under the paper and a segmented backing electrode above it. The charge image is built up on the paper, then the toner is flowed over it and the carbon (I assume) particles adhere to the charged bits. No drying heater in mine. -tony
[cctalk] Re: Seeking out Joe Rigdon / John Lawson
On Thu, Apr 4, 2024 at 1:48 AM Sellam Abraham via cctalk wrote: [Sent privately] > > Has anyone communicated with or know a way to communicate with Joe Rigdon > out of Florida? Most here should know him as an old-school ClassicCmp > veteran. I have just heard that he attended the HP Handhelds conference last year so is alive and well and still, presumably, interested in such machines. But no way to contact him -tony
[cctalk] Re: DEC VT340/330 ROM Cartridge
On Sat, Apr 6, 2024 at 3:54 PM Douglas Taylor via cctalk wrote: > > The DEC VT340 has a slot in the back of the terminal to insert a ROM > cartridge. I can't find any description of what this DEC labeled ROM > cartridge would do for you. I've seen them with V1.1 and V2.1 markings, > does anyone remember what additional capabilities these ROM cartridge > provide? Will the terminal work at all without that cartridge fitted?. I've had a quick look at the VT330 and VT340 printsets and I can't obviously spot any firmware ROMs on the main board schematics. So my first guess is that said cartridge is the terminal firmware. -tony
[cctalk] Re: Seeking out Joe Rigdon / John Lawson
On Fri, Apr 5, 2024 at 1:33 PM Tony Duell wrote: > > On Thu, Apr 4, 2024 at 8:58 PM Zane Healy via cctalk > wrote: > > > Have you checked with Eric Smith or Dave McGuire? I want to say that Dave > > was in the same general area as Joe when he lived in Florida. > > I've asked Wlodek Mier-J of the British HPCC calculator club if he has > any contact details. Unfortunately Wlodek has been unable to contact Joe Rigdon as well. -tony
[cctalk] Re: Seeking out Joe Rigdon / John Lawson
On Thu, Apr 4, 2024 at 8:58 PM Zane Healy via cctalk wrote: > Have you checked with Eric Smith or Dave McGuire? I want to say that Dave > was in the same general area as Joe when he lived in Florida. I've asked Wlodek Mier-J of the British HPCC calculator club if he has any contact details. -tony
[cctalk] Re: DEC Processor Books
On Sun, Mar 17, 2024 at 3:38 PM Adrian Godwin via cctalk wrote: > > HP at least sometimes used staff. There's one HP publicity photo I remember that I surely hope was staged. It's for the HP9880 hard disk system for the HP9830 calculator. The disk drive is an HP7900, a fixed/removeable platter drive somewhat similar to an RK05. It the photo there's man next to it smoking a pipe. A darn good way to get a headcrash. -tony
[cctalk] Re: VCF SoCal
On Wed, Feb 21, 2024 at 9:39 AM Stefan Skoglund via cctalk wrote: > > Liam, TriPOS ? > > If i'm not wrong it was a OS developed in Cambridge (Cambridgeshire). It was. The name came from the fact that a course at Cambridge University is called a Tripos. Originally written by Martin Richards (as in BCPL) > > Did someone port it to other arch than ARM ? The oldest version I know of ran on PDP11s. I am pretty sure there was a 68000 version at one point too. -tony
[cctalk] Re: Unknown Viewsonic monitor flashes Red-Blue-Green-White
On Fri, Dec 1, 2023 at 4:22 AM Chuck Guzis via cctalk wrote: > > On 11/30/23 15:46, Van Snyder via cctalk wrote: > > I was given a 22-inch Viewsonic monitor. The label had been scratched > > off. It has four switchesd below the screen, labeled 1, 2, an up arrow, > > and a down arrow. > > > > When I plug it in, it flashes Red, Blue, Green, White at about one- > > second intervals. Pushing the buttons doesn't affect it. > > > > I haven't attached a VGA or DMI to it. > > > > Is it irreparably broken? > > Short answer--no, it's not irreparable if it's showing life. Anything can be repaired :-) If it was made once it can be made again > > This sounds like a power supply issue, but that's just a guess. > I wondered if it was trying to set the operating voltages (g2 voltage) of the three electron guns by turning each on in turn and measuring the beam current. And then failing for some reason. The fact you get all 3 primary colours suggests the CRT is good enough to do something but maybe not good enough for this automatic set-up to work. Or more likely there is a fault in that system. -tony
[cctalk] Re: VT100 Monitor Board
On Wed, Nov 29, 2023 at 6:16 PM Rob Jarratt wrote: > I am working on the schematic and when it is done I will post it for > information. However, I was wondering what you suggest for testing the board > once I have done this. Simply replacing the blown fuse and plugging it in > doesn't sound like a good idea. Equally, not sure if using the light bulb > method for limiting current into the PSU is going to help is it? You could try a lamp limiter between the 12V power supply and the monitor board (or across the (empty) fuseholder). Something like a car headlamp bulb with both filaments in parallel. -tony
[cctalk] Re: VT100 Monitor Board
On Sat, Nov 25, 2023 at 11:12 PM Rob Jarratt wrote: > > Have you checked the diodes and capacitors associated with the flyback > > transformer? If something is shorted there. it's the equivaent of running a > > power supply into a short circuit. The input current will go up. > > I have checked all the diodes (in circuit) and they appear to be OK. One > capacitor may be suspect but without the full schematic I am not sure. I may > have to lift it to check. Without the schematic you are going to have problems. With a schematic you can see (a) Can you isolate certain areas -- for example the vertical deflection syste > > Trace out a schematic of the board so I know what I am dealing with. > > Yes, I may have to do that. Historically I have done a poor job of this > because of my insufficient understanding of electronics. It gets easier with experience. Looking at every small monochrome monitor schematic you can find will give you an idea of the sort of things to look for. > > I do wonder what the problem is with testing it with the flyback connected, > > though... > > Only that I know it can produce lethal voltages and I would rather avoid that > if I can. The high voltage outputs can't supply that much current and are unlikely to be lethal. Mains, and even worse the rectified mains in an SMPSU, is a lot more liely to kill you. That said, work with one hand in your pocket (current flow arm-to-arm is the most dangerous) and take care. I don't see how you can debug a monitor without having the flyback in place. It's part of the highest power circuit on the board. And it provides voltages for many other areas. -tony
[cctalk] Re: VT100 Monitor Board
On Sat, Nov 25, 2023 at 12:07 PM Rob Jarratt via cctalk wrote: > > Hello, > > > > As some may recall I have been working on getting a VT100 going again. I > have made good progress and I think the main board is probably OK now (see > here if you are interested: > https://robs-old-computers.com/2023/11/19/vt100-keyboard-constant-clicking-f > ault/). Possibly I still need to replace the NVRAM, but I am leaving that > until I fix the problem I want to describe next. > > > > The problem is that there is no image on the screen. This is because the > monitor board is not doing anything, there is no glow from the neck of the > tube etc. I have found that this is because the fuse on the 12V input to the > monitor board is open circuit. OK. My first suspicion would be problem round the horizontal output stage/flyback transformer. But that is just a guess > > > > Of course the worry is, why? There could be a fault on the board. I have > tested the transistors in circuit with a multimeter and they appear to be > OK. I used a bench PSU to give the board 12V and it drew no current (with > all connectors disconnected). I tried again with the round connector > attached to the end of the tube and it drew about 100mA and there was a > faint glow from the neck of the tube. The CRT has a heater fillament rated at about 11V or so. Most, if not all, such monitors run it from the12V input via a suitable resistor. So you know the CRT filament is good but you don't know much else so far. > > > > I am hesitant just to replace the fuse and try it. I am hoping for some > suggestions on how to test this safely (in particular without involving the > flyback transformer) to find if there is a fault. I don't think you can do much without the flyback connector plugged in. You need the flyback transformer to do any sane tests on the horizontal side, and you need the iron-cored inductor, normally wired on the same connector, to get the vertical output stage to work. Also you may need the deflection yoke connected for some tests, the inductance of the horizontal deflection windings can make quite a difference (factor of 2) to the voltages produce by the flyback. The flyback transformer started as a 'something for nothing' idea. To deflect the electron beam horizontally, you store considerable energy in the horizontal yok windings. Rather than waste that at the end of the line, you use it to power other bits of the monitor, like the EHT for the CRT final anode. Have you checked the diodes and capacitors associated with the flyback transformer? If something is shorted there. it's the equivaent of running a power supply into a short circuit. The input current will go up. Does this unit have a horizontal oscllator? Quite a lot do not, they simply use the horizontal pulses from the logic,suitably amplified, to drive the horizontal output transistor. This could never have worked for television as interference pulses could send the thing crazy with voltages going all over the place, but it's not uncommon in small monitors. The IBM5151 was like that. If there is no horizontal oscillator then you need to provide a drive signal of the correct frequency and duty cycle. Rather than use the logic (which might be faulty and thus mis-driving the monitor), I've been known to cobble something up using a 555 timer chip, Here's roughtly what I would do : Trace out a schematic of the board so I know what I am dealing with. Check all diodes and capactiors hung off the flyback transformer. Ring-test the flyback transformer. Make a test oscillator to drive it if necessary Connect it up, run it from a current limited supply. If it tries to draw too much current, then I've mssed something. Might try lifting the diodes to disconnect voltage outputs to see if one of those is loading it. I do wonder what the problem is with testing it with the flyback connected, though... > > > > For information, the monitor is an Elston and I pre-emptively replaced all > the electrolytics on the monitor board apart from the non-polar one. Why? I have never understood replacing capacitors at random in the hope it cures the fault. It is much easier to start from a board that once worked and trace the fault. -tony
[cctalk] Re: Microcom S-64 8085 system
On Sun, Oct 1, 2023 at 8:38 AM Wouter de Waal via cctalk wrote: > > Hi all > > I re-discovered some eurocards I found in a box at a swapmeet long ago. > > It looks like a complete 8085 system. Lots of RAM, 2K EPROM, I/O, FDC. > > The strange thing is that the EPROM is mapped at F800, the code in there > looks like 8085 code, and looks like it wants to live at F800. And there's > RAM at . It might have run CP/M (which will run on an 8080, and therefore on an 8085). That needs RAM at location [1]. If the EPROM is mapped to F800 only (some machines mapped it to as well after a reset, this image was disabled after the processor jumped to F800 or wherever) then there might be a bit of logic to force a jump instruction onto the data bus after a reset to get the processor to run the code in the EPROM. [1] For the pedants, there were 'relocated versions of CP/M that could run on machines like an unmodified TRS-80 model 1 with ROM at location 0. These versions needed special relocated versions of all the application software and were generally pretty useless. -tony
[cctalk] Re: Silly question about S-100 and video monitors
On Fri, Sep 1, 2023 at 6:29 PM Rick Bensene via cctalk wrote: > > Tony wrote: > > > Didn't Singer own Friden (or at least the name) at one point? I am sure > > I've seen calculators > > batched(sic) 'Singer Friden'). > Singer effectively began the death of internal electronic calculator > development at Friden when it quietly started selling the transistorized > Friden 1112 electronic calculator, which was made in Japan by Hitachi, > purchased under a temporary OEM agreement between Singer and Hitachi. > > The 1112 was an experiment to see how well the machine sold. It did > reasonably well, and that was enough for Singer to slowly begin to dismantle > the Friden electronic calculator development operation, and start selling > OEM-acquired (from Hitachi initially) calculators under the Singer/Friden > badge. By coincidence I bought a Hitachi KK521 (later version with vacuum fluorescent display tubes, not Nixies) a couple of weeks back. I read that it was also sold as the Friden EC1117A. -tony
[cctalk] Re: Silly question about S-100 and video monitors
On Fri, Sep 1, 2023 at 4:51 PM dwight via cctalk wrote: > > My first computer was a Poly-88. I had no monitor and no keyboard. > I read and understood the instructions about finding a TV that used a > transformer power supply. Many newer TV's of that day were not using a > transformer for the main supply. I went to several secondhand stores and > found one that would work. The original TRS-80 model 1 monitor was based on a live-chassis (hot chassis?) RCA TV set. The USA version had an optoisolator circuit on the video input, the LED driver circuit was powered from the +5V line in the computer (hence the +5V on one pin of the video DIN socket). As the TV was designed for 115V mains only, the European version has a step-down transformer on the AC input. They used an isolating transformer, meaning there was no need to isolate the video input in the European models. Philips made a viewdata termal set where the colour monitor was a modified KT3 television. The power supply in that starts by bridge rectifying the mains input, meaning the chassis is dangerously live no matter which way round the mains is connected. The solution to that was a 240V 300mA (or so) secondary winding on the mains transformer in the the viewdate terminal unit. This provided an isolated AC supply to the monitor, so the chassis of the latter could be earthed. > The keyboard was from a surplus Singer data entry machine ( I thought they > only made sewing machines ). Didn't Singer own Friden (or at least the name) at one point? I am sure I've seen calculators batched 'Singer Friden'). And I have a telecoms test tone genrator that's badged 'Singer' (I assume the same company) -tony
[cctalk] Re: Silly question about S-100 and video monitors
On Fri, Sep 1, 2023 at 4:31 PM dwight via cctalk wrote:
>
> I do understand the warranty sticker. Say we have the average computer buyer.
> He has a screw driver and mostly knows how to use it. He also went to Radio
> Shack ( long gone ) and bought a cheap soldering iron. He is now fully
> equipped to repair what ever is wrong with his box. ( obviously not at Tony's
> level of competence ) He takes the cover off and has no idea what he is
> looking at or what he is looking for. ( I think we have all been there at one
> time ) He sees something with a screw driver slot. He has a screw driver.
> Perhaps all it needs is a minor adjustment. He turns the screw one way, and
> nothing changes. He turns it the other way and, pop, some smoke comes out of
> the other side of the chassis.
You clearly know the TRS-80 Model 1 (or are a good guesser).
There are 4 presets ('things wth a screwdriver slot) on the Model 1
logic board. Two of them are associated with delays on the horizontal
and vertical sync signals. Adusting those can cure a
video-going-off-screen issue.
The other 2? They set the output voltage of the +12V and +5V
regulators. There is no overvoltage protection on the former, turn
that too hgh and you may wipe out all the DRAMs. The latter has a fat
zener across the output, but I am not sure I trust it. And if you turn
the +5V line up you could be looking to replace a lot of ICs...
-tony
[cctalk] Re: Silly question about S-100 and video monitors
On Thu, Aug 31, 2023 at 9:53 PM Chris Zach via cctalk wrote: > > Which is weird, since Radio Shack was renowned for putting schematic > diagrams on so many of their products. My Flavoradio still has the > schematic on it if a transistor goes bad And they would sell spare parts and service manuals for just about everything they sold. Their pocket computers were of course essentially re-badged Sharp and Casio machines. Getting the service manuals from the original companies was moderately harder than getting defence secrets. Getting the manuals from Tandy/Radio Shack was simply a matter of ordering them at the local shop. -tony
[cctalk] Re: Silly question about S-100 and video monitors
On Thu, Aug 31, 2023 at 7:49 PM Fred Cisin via cctalk wrote: > On Thu, 31 Aug 2023, geneb via cctalk wrote: > > Fun fact - the "Warranty Void if Removed" tags were and are illegal. The > > warranty can only be voided if the mfgr can prove the thing you did resulted > > in the problem you're claiming warranty on. :) > > eventually codified in the Magnuson-Moss warranty Act, enacted in 1975, > just a few years before RS started pasting those stickers on.. > > But, they didn't say that modifications voided the warranty, . . . > the warranty was only voided if the sticker was damaged. I would love to know how removing an external sticker over a screwhead (and doing nothing else) could cause an IC inside the machine to fail. As the latter is the sort of thing you claim warranty on, removing the sticker have no bearing on the validity of said warranty. I did manage to get one of those stickers off in one piece. I stored it on the backing paper of some rub-down letter transfers (remember those?) and never put it back after I completed the modifications/repairs. My idea was I'd put it on a unit I'd been inside if I did want to claim on th warranty. Never did that, I might still have it somewhere. -tony
[cctalk] Re: Connecting MFM emulator as both 1st and 2nd drive in Microvax 2000?
On Sun, Aug 13, 2023 at 5:20 PM Nigel Johnson Ham via cctalk
wrote:
> The DEC Rainbow RX50s only have one motor :-)
{being pedantic}
No they don't. They have 2. A permanent-magnet DC motor used to drive
both spindles and a stepper motor used to position both heads.
But I will agree it is a lot more usual for a dual floppy drive to
have separate spindle and positioner motors for the 2 disks
(Actually don't the Persci dual 8" drives with voice coil positioners
have a common spindle motor and head positioner for the 2 disks?)
-tony
[cctalk] Re: 50 pins in three rows
On Sat, Aug 12, 2023 at 4:36 AM Chuck Guzis via cctalk wrote: > > On 8/11/23 16:08, Fred Cisin via cctalk wrote: > > > > Or, is it correct to refer to anything between DA and DB as "DB"?? > > (such as "DB-23" on Amiga? Yes, I dremeled a DB25 to fit.) > > Atari ST also used strange shell/pin count connectors. Calling them DB > is obviously not correct--calling them DB-ish might be closer to fact. > FWIW, they're pretty hard to find nowadays. I've seen DF19 and DG23, which makes sense. Originally there were the DA to DD shell sizes. The DE9 came later and used the next letter for its size. So 2 more new sizes get the next 2 letters. -tony
[cctalk] Re: VCF Southwest 2023 some highlights
On Tue, Jun 27, 2023 at 12:35 AM Mark Huffstutter via cctalk wrote: > I've never seen an HP-9830A that gorgeous, and with the > Companion HP-9866A printer no less, wow! What I'd like to see is an HP9830 with the HP9880 disk system (an HP7900A drive with a special controller). Any still working? -tony
[cctalk] Re: Need AUI cable
On Wed, Jun 28, 2023 at 5:02 PM Chris Zach via cctalk wrote: > Yup, it's a DEC thing, however the DEQNA cab kits do the proper cam and > lock interface. I thought about removing the nuts, but went with > ordering a cable and I'll pull the studs off it to make it work. Sub > optimal but that is DEC (also I remember AUI cables did come with screws > so other vendors did this in the early days as well) Classic PERQs certainly did (4-40 UNC jackposts and screws rather than the slidelock). That's one reason I had to make my own AUI cable. Of course a couple of weeks later I spotted a couple of cables with DA15 connectors being thrown out. I grabbed them, they turned out to be genuine ICL PERQ AUI cables... -tony
[cctalk] Re: Need AUI cable
On Wed, Jun 28, 2023 at 2:44 PM Jonathan Chapman via cctalk wrote: > > > For a few inches, which would be enough here I think, I've used an IDC > > DA15 plug and socket crimped onto the normal ribbon cable. Technically > > it's wrong but the reflections on that length of cable won't matter. > > That's how Sun VME Ethernet boards are set up, the board itself is way back > near the VME connectors and small (or a Multibus in a converter, and small). > Can't be too bad if Sun did it on serious business workstations, right?! > As a PERQ-fanatic, I'd better not give my prejudiced views on Sun :-) But seriously. Sun machines work on the ethernet just fine. So it shows you can break the rules a bit... -tony
[cctalk] Re: Need AUI cable
On Wed, Jun 28, 2023 at 6:00 AM Grant Taylor via cctalk wrote: > > Tony's email makes me ask more questions than I have (smart alack) > answers to. Maybe ~> hopefully I can ~> will learn something. I was being a bit of a smart alec too. The point I was making is that a bit of normal IDC ribbon cable is not electrically the correct cable for an AUI interface but it won't matter over a few inches. The correct cable is 4 twisted pairs with a overall screen (shield). One pair is thicker wires than the other 3 and is used for the power. This cable was very hard to get by the metre when I needed some about 30 years ago, and a full reel was several hundred pounds. I was lucky enough to be given a couple of metres as an 'offcut' by a gentleman who worked in network support. You probably need something like that if you're makng a 1m cable. But not for what the OP is trying to do. > > On 6/27/23 10:26 PM, Tony Duell wrote: > > For a few inches, which would be enough here I think, I've used an IDC > > DA15 plug and socket crimped onto the normal ribbon cable. Technically > > it's wrong but the reflections on that length of cable won't matter. > > Isn't 10Base quite resilient? Especially at these distances? There are 2 problems with the wrong cable. Firstly will it carry the current for the power supply pins? My experience is that it will, at least for most transceivers. The second is that the characteristic impedance is wrong. It's actually not too far off but... This will cause reflections. It won't matter on a few inches as the reflections will take about a nanosecond to get back and will die out in << the bit time. It may matter on longer cables. > > Though I don't know if AUI is considered 10Base in and of > itself. Doesn't it become 10Base5 / 10Base2 / 10Base-T based on what > transceiver is on the other side of / attached to the other end of the > AUI cable? AFAK AUI is not 10baseAnything for the reason you give > > I'm assuming that MAU is meant for multiple stations to connect an AUI MAU is something like 'media access unit' and is the official name for a transceiver. Due to the fact that there had to be a certain distance between transceivers on the cable, there were things that had multiple AUI connectors to link to computers (these were normally male DA15s on the unit, so a normal transceiver cable would work) and a further AUI connector (normally a female DA15) for a transceiver onto the 'real' ethernet. DEC's DELNI is a common-ish example of such a unit, I think the printset is on bitsavers > cable into and it then connects to the ostensibly 10Base > network. -- I originally read and was replying as if Chris was trying > to take the AUI port on his Pro/380 and connect it to an AUI port on a > hub / switch. My concern being that both AUI ports would be the same > gender and assuming that there are (at least) a pair of transceivers > converting each device from AUI to 10Base to connect to each > other. There is no real equivalent of an 'AUI null modem cable' (should that be 'null transceiver cable'?) If you want to link 2 computer-type ports together you need the equiavelent of 2 transceivers. Probably the easiest is a pair of 10baseT transceivers and a crossover 8p8c cable If you want to link 2 transceivers together on the AUI side then that's a network bridge. Even a basc one is quite a lot of electronics. If you want it to only pass on packets for particular machines then it gets very complicated, one that I picked up last year contains a 68020 CPU _and_ a board containing a 16 bit processor made from 2900-series bitslice stuff -tony
[cctalk] Re: Need AUI cable
On Wed, Jun 28, 2023 at 6:13 AM Fred Cisin via cctalk wrote: > With many boxes of used cables, often there will be cables that are DB-25, > but with 16 pins missing in the 25 pin connector, often leaving pins 1-8 > and 20, and gaps where other pins could have been.. I call THAT a DB-9 > The DE9 serial port includes RingIndicator (pin 22 on the DB25 one) but not protective ground (pin 1 of the DB25). I've found a number of cables that therefore wire 10 pins -- 1-8,20,22. You can call that a DB10 if you like (I don't) -tony
[cctalk] Re: Need AUI cable
On Wed, Jun 28, 2023 at 1:19 PM Paul Koning via cctalk wrote: > > > > > On Jun 28, 2023, at 1:13 AM, Fred Cisin via cctalk > > wrote: > > > > DA, DC, DE connectors are a different size D shell than the DB, which is > > the one commonly used for a 25 pin cable. > > There is also DD, though I've never seen one in the wild. DA is the shell > for AUI connectors, DC is used for RS-422 (37 pins) I think. The DD50 (standard density) has been used for SCSI-1 (maybe old Sun machines?) amongst other places. I've certainly used them. I did once fit an ST412 interface onto a DD50 socket. There's a total of 54 wires on the 34 pin control and 20 pin data cables of course but enough wires unused on the latter than you can get away with 50 pins. I've seen a DD78 on some HP device but I forget what. DC37 was used for RS449, PC external floppy drives,etc. DC62 was the connector for the IBM5161 expansion unit. There are DA26 and DB44 connectors but I don't think I've ever used them. FWIW I have seen Centronics parallel interfaces on DA15 connectors (there are enough pins for 8 data lines, strobe, busy, ground and a few other signals). There is NO standardisation, I've got a Tandata videotext terminal, a Philips videotext terminal and an HP2225P printer here and they don't even agree on the ground and data lines. -tony
[cctalk] Re: Need AUI cable
On Wed, Jun 28, 2023 at 2:17 AM Chris Zach via cctalk wrote: > > Anyone in MD got an AUI cable (few feet long) I can steal so I don't > have to remove the bolts from the Pro/380's Ethernet socket or the pins > on my 10bt ethernet MAU? For a few inches, which would be enough here I think, I've used an IDC DA15 plug and socket crimped onto the normal ribbon cable. Technically it's wrong but the reflections on that length of cable won't matter. -tony
[cctalk] Re: H7819-AA / VAXstation 4000/90 and 4000/96
On Mon, Jun 26, 2023 at 3:38 PM Jan-Benedict Glaw via cctalk wrote: > > Hi! > > As I'm preparing to setup my old hardware, I fetched two VAXstations > (4000/90 and /96) from storage and cleaned one of them throughoutly. > > Then I gave power (to both of them), but both won't really start: > all 8 diag LEDs are on (--> power available but CPU didn't start > executing instructions.) > > I took the PSU (from the cleaned /90), a DEC H7819-AA, and measured > it. Unfortunately I didn't find pinouts or schematics at a first > search. The plate states that there should be 3.3V, 5V, 12V, -12V and > -9V. I found most of that: > > > +--+ > |o | > | DEC H7819-AA PSU 10 +---+ 1 | > | (view at the bottom side) | | | > | | | | > | | | | > | 18 +---+ 9 | > |o | > |+---++---+| > || Fan || Fan || > ++---++---++ > > With above pin numbering, this is what I could find / measure / deduce: > > 3V3 brown 10 1 blue12V > 3V3 brown 11 2 black GND > GND black 12 3 red 5V > GND black 13 4 red 5V > GND black 14 5 black GND >5V red 15 6 black GND >5V red 16 7 white -12V >5V red 17 8 blue (0.78V) >(4.91V) lilac 18 9 brown (-1.65V) > > Most values look plausible, except those three in parentheses. At > least one of them should probably be -9V wrt. GND I guess, but that's > totally absent. And what's the other two? (If I got the colors wrong: > Please forgive, I'm red-green blind.) That could be some "power-okay" > indicator, or external switch-off? I don't know this machine at all (too modern :-)) but that -9V sounds at thought it might be for an internal ethernet transceiver. Now an ethernet transceiver is supposed to be isolated from ground and one way of helping with that is to have a totally isolated 9V output on the power supply with its own 'ground', not connected to the ground for the rest of the supplies. Using a high impedence voltmeter like most DMMs, you'd see random noise voltages on those 2 lines wrt the normal ground. What voltage do you measure between the suspect blue and brown wires? Connect your meter between them, not to the black ground and something else. -tony 'There is no such thing as ground' -- Don Vonada
[cctalk] Re: VCF Southwest 2023 some highlights
On Mon, Jun 26, 2023 at 1:06 PM Steve Lewis via cctalk wrote: > > VCF SW was this past weekend near Dallas, Texas. > > Here are some highlights from my perspective. > > https://voidstar.blog/vcf-southwest-2023/ > > > Most photos you can click to enlarge (Edge has bugs with WordPress, you may > need to scroll up/down a little bit to get the click thing working) I may be talking nonsense, but you describe the Tektronix 4054 as a 6800-based system. I thought the 4051 used that processor, but the 4052 and 4054 used a board of AM2900-series bitslice chips that implement a processor with an instruction set similar to the 6800 but with no BCD operations and some 16 bit extensions. -tony
[cctalk] Re: Rainbow H7842 PSU Fault
On Sun, Jun 25, 2023 at 5:52 PM Rob Jarratt wrote: > > Before I confuse matters too much I should point out that I was not using the > Rainbow power switch unit but one from a DECmate. I had erroneously thought > there was a fault with the Rainbow one. I think the fan supply may be > different on the DECmate switch, so ignore the bit about the fan turning. It appears that there are 2 ways of powering (different types of) fans with this power supply. Whether one was used in the Rainbow and the other in the Decmate I know not. But anyway : A 12V DC fan running off the DC output of the power supply. This is the one shown in my schemtic for the supply. Note the jumper link in the fan power plug that means the supply doesn't get mains if you forget to plug the fan in. A 115V AC fan connected to the unused pair of pins on the AC input cable to the power supply (top right of the 'switch/fan assy' in my schematc. This uses the primary winding of the startup transformer as an autotransformer on 230V mains. Note that the latter fan will run if the chopper side of things is dead, the former won't. -tony
[cctalk] Re: Rainbow H7842 PSU Fault
On Sun, Jun 25, 2023 at 5:33 PM Rob Jarratt wrote: > > Thanks Tony. I removed the mains bridge rectifier and found it measured short > across two of its terminals, so I am ordering a replacement. I tested the > PSU, without the mains bridge rectifier and without the diodes on the output > of the startup transformer. I got 24VAC on the output of the , the lamp > limiter bulbs did not light and the fan in the power switch unit turned. So > it looks like the startup transformer is actually OK. > It's possible that the rectifier just failed. Or it might have been damaged because it had to pass too much current due to a problem in the main chopper circuit. I would certainly check the chopper transistor for shorts now. -tony
[cctalk] Re: Rainbow H7842 PSU Fault
On Sun, Jun 25, 2023 at 1:36 PM Rob Jarratt via cctalk wrote: > > Hello, > > It has taken me ages to get back to this, but I think I have hit an > insurmountable problem. > > I reassembled the PSU after the PWM started working again and tested it with > a dummy load and using two 100W light bulbs in series on the input side to > limit the current. However, it did not work. I traced this to the 7812 > regulator that supplies Vstart (PSU Sheet 1) not getting enough voltage to > run, about 3.7VDC. In the same conditions the working one gets about 10 or > 11VDC. I also noticed that on the good PSU the 100W bulbs pulsed and were > fairly dim, but on the bad PSU they were brighter and glowed steadily. > > This made me suspect that the startup transformer may have been damaged. So > I checked the output of the startup transformer. On the bad PSU this was > about 2.4VAC, while on the working one it was about 12VAC. I lifted all 4 of > the diodes connected to the startup transformer and they all tested OK. > > Sadly, I think this means the transformer must have been damaged. I have the > facility to do a ring test on the transformer, but don't want to remove it > unless there is a need to. Is there any other failure mode that I am not > considering? I didn't check the inputs to the transformer, so something > could be short on the input side and pulling the input to the startup > transformer down. It is worth reminding anyone reading this, that the 7812 > on PSU Sheet 1 did fail with a short to ground. I wouldn't be too hasty to condemn the transformer. This is a mains transformer, not part of a switch mode power supply circuit. It takes in mains via the voltage selector switch, the centre tapped secondary is full-wave rectified twice to produce the +12V and -12V rails needed to get the rest of the supply going. Now, you mention the lamp limiter bulbs (series light bulbs, whatever you call them) are bright. That means they are dropping significant voltage. So the input voltage to the startup transformer will be less than mains. Which will lead to a low output from its secondary winding. Try disconnectng the mains feed to the main chopper circuit. Perhaps remove the mains bridge rectifier, or both of the inrush limiter thermistors. Anything to prevent power getting to the main chopper circuit. Power up again with the lamp limiter in series with the mains (of course). My guess is that then the bulbs will be dark and the startup transformer will give the right voltages. This would point to a problem with the chopper circuit. -tony > > I have included a couple of minor responses to Brent's last email to me > below. > > Regards > > Rob > > > -Original Message- > > From: Brent Hilpert > > Sent: 26 May 2023 17:24 > > To: r...@jarratt.me.uk; General Discussion: On-Topic and Off-Topic Posts > > > > Subject: Re: [cctalk] Rainbow H7842 PSU Fault > > > > On 2023-May-25, at 1:43 PM, Rob Jarratt via cctalk wrote: > > > > > > This evening I went to check Vstart for any oscillation. However, all of > a > > sudden, the current draw is down to 85mA and PWM has started working. I > > am at a loss to explain it. I wondered if there might be a dry joint, but > I have > > tried a few light taps and shakes and it continues to work. Perhaps your > idea > > of some debris causing a short might explain it, otherwise I just don't > know. > > > > Operation with only VStart+12 places the circuitry into an unspecified > > operating region - a region outside of the design intentions. In part, > several > > semiconductor junctions and portions of circuitry are polarised opposite > to > > their normal/designed-for state. It is not surprising that you are seeing > > odd/unpredictable behaviour under this operating environment, nor is it > > surprising that it's different than the 'good' supply under the same > operating > > environment. > > > > So why was it in shutdown earlier the other day but not now? : > > Who knows - it's operating in an unspecified region. Perhaps the room > > temperature is 2 degrees higher. That's a serious point, not phase-of-the- > > moon satire. > > Well, the weather here has indeed got a bit warmer. > > > > > When you supplied the proper startup environment with both Vstart+12 and > > Vstart-12 both the bad and good unit behaved as expected for the design. > > > > Why is the VStart+12 current draw higher when it was in shutdown versus > > when the PWM controller IC is pulsing? : > > Because in shutdown the 'Chopper Driver' transistor (PSU Sheet 2) is held > > hard ON (conducting) (see datasheet). > > Holding this transistor ON subtracts it's off-state current (~ 17mA) but > adds > > it's on-state base current (~ 37mA) and it's on-state collector current (~ > > 73mA), for a net up-to ~ 93mA increase (may be less dependant on duty > > cycle of PWM), to the Vstart+12 current. > > > > Thanks for explaining that, it makes more sense now. I need to learn to look > at other parts of the schematic beyond
[cctalk] Re: Greaseweazle part 2
On Sun, Jun 25, 2023 at 8:31 AM r.stricklin via cctalk wrote: > > > > On Jun 24, 2023, at 11:10 PM, Tony Duell via cctalk > > wrote: > > > > And this is where I get lost.. > > > > I do not understand your overbearing attitude of helplessness toward this > project. I have known you on many occasions to go to far greater lengths to > achieve far deeper understanding of far more complicated devices. Far less > intelligent people than you have managed somehow to marshal the necessary > resources to make useful headway with the damn thing. The majority of the > questions you’re demanding answers to seem to me like the kind of questions > that could be easily answered with about four minutes’ worth of simple > experimentation. It's a combination of things : I regard the Greaseweazle (or any other similar device) as a tool to help me to do something which I enjoy -- running classic computers. While I am happy to spend time improving my skills at using tools, I do not expect to have to guess at what the designer was doing. I also want to understand what my tools should be doing. Not what they seem to have done in the past. Getting some of my classics running is a big enough ob without having to worry whether or not some missing option in writing the boot disk image to a real disk has caused that disk to be mangled. The more I know to be correct, the better. I can sit down with the Greaseweazle board, the PC, a floppy drive and a logic analyser and probably find some combination of options that produces what look to be sensible signals on the Write Data line. But whether they are sensible signals is a much bigger problem. Yes, I like solving puzzles. But this shouldn't be a puzzle. If I want to solve a puzzle about reading and writing arbitrary disk formats the I'll design my own device to do it. -tony
[cctalk] Re: Greaseweazle part 2
Still trying to make sense of this thing. The problem is that one very important thing is missing. I refer to DODUMENTATION. I don't fall for this modern rubbish that a product with a thin manual is easy to use. No, the thicker the manual the better. It will probablt answr my questions. But the Greaseweazle has no documentation at all other than the built-in help, (which is what I'd expect, a reminder of the options if you know the product and can't remember the exact term used to, say, check the drive speed). If I type 'gw' at a command prompt I get the following, which at least gives the options. -- C:\classic_computer\greaseweazle\greaseweazle-1.13>gw Usage: gw [--time] [action] [-h] ... --time Print elapsed time after action is executed -h, --help Show help message for specified action Actions: infoDisplay information about the Greaseweazle setup. readRead a disk to the specified image file. write Write a disk from the specified image file. convert Convert between image formats. erase Erase a disk. clean Clean a drive in a zig-zag pattern using a cleaning disk. seekSeek to the specified cylinder. delays Display (and optionally modify) drive-delay parameters. update Update the Greaseweazle device firmware to latest (or specified) version. pin Change the setting of a user-modifiable interface pin. reset Reset the Greaseweazle device to power-on default state. bandwidth Report the available USB bandwidth for the Greaseweazle device. rpm Measure RPM of drive spindle. - I can basically understand that So lets see how to write an image to a disk . I type gw write -h and get : - C:\classic_computer\greaseweazle\greaseweazle-1.13>gw write -h usage: gw write [options] file Write a disk from the specified image file. positional arguments: file input filename options: -h, --help show this help message and exit --device DEVICE device name (COM/serial port) --drive DRIVEdrive to read (default: A) --diskdefs DISKDEFS disk definitions file --format FORMAT disk format --tracks TSPEC which tracks to write --pre-erase erase tracks before writing (default: no) --erase-emptyerase empty tracks (default: skip) --fake-index SPEED fake index pulses at SPEED --no-verify disable verify --retries N number of retries on verify failure (default: 3) --precomp PRECOMPwrite precompensation --dd DD drive interface DD/HD select (H,L) DRIVE: Drive (and bus) identifier: 0 | 1 | 2 :: Shugart bus unit A | B :: IBM/PC bus unit SPEED: Track rotation time specified as: rpm | ms | us | ns | scp | TSPEC: Colon-separated list of: c=SET :: Set of cylinders to access h=SET :: Set of heads (sides) to access step=[0-9] :: # physical head steps between cylinders hswap :: Swap physical drive heads h[01].off=[+-][0-9] :: Physical cylinder offsets per head SET is a comma-separated list of integers and integer ranges e.g. 'c=0-7,9-12:h=0-1' FORMAT options: acorn.adfs.160acorn.adfs.1600 acorn.adfs.320 acorn.adfs.640acorn.adfs.800acorn.dfs.ds acorn.dfs.ss akai.1600 akai.800 amiga.amigadosamiga.amigados_hd atari.90 atarist.360 atarist.400 atarist.440 atarist.720 atarist.800 atarist.880 coco.decb coco.decb.40t coco.os9.40ds coco.os9.40ss coco.os9.80ds coco.os9.80ss commodore.1541commodore.1571commodore.1581 dec.rx01 dec.rx02 dragon.40ds dragon.40ss dragon.80ds dragon.80ss ensoniq.1600 ensoniq.800 ensoniq.mirage gem.1600 ibm.1200 ibm.1440 ibm.160 ibm.1680 ibm.180 ibm.2880 ibm.320 ibm.360 ibm.720 ibm.800 ibm.dmf ibm.scan mac.400 mac.800 mm1.os9.80ds.hd32spt mm1.os9.80ds.hd36spt msx.1d msx.1dd msx.2dmsx.2dd occ1.dd occ1.sd olivetti.m20 pc98.2d pc98.2dd pc98.2hd pc98.2hs raw.125 raw.250 raw.500 sci.prophet sega.sf7000 tsc.flex.dsdd tsc.flex.ssdd zx.trdos.640 Supported file suffixes: .a2r .adf .ads .adm .adl .d64 .d71 .d81 .d88 .dcp .dim .dsd .dsk .edsk .fdi .hdm .hfe .ima .img .imd .ipf .mgt .msa .raw .sf7 .scp .ssd .st.td0 .xdf And this is where I get lost.. What are all the file suffixes (extensions?) Does the program determine the file type from that?What does each
[cctalk] Re: Greaseweazle part 2
On Mon, Jun 12, 2023 at 7:08 AM Tom Hunter via cctalk wrote: > > Is it really necessary to be always so confrontational? It is unpleasant. Could you please indicate exactly which statement in my original message you object to? [And please don't top-post. It's annoying] -tony > > On Sun, 11 June 2023, 10:44 pm Tony Duell via cctalk, > wrote: > > > > Fundamentally, it seems to me that they're all the same basic hardware, > > > timing intervals between flux transitions. > > > > > > So other than the soaftware, what's the difference? > > > > I could make a stupid comment and ask 'what's the difference between a > > PDP8, PDP11, PERQ or HP9830?'. Apart from having finite memory, all > > are (I believe) equivalent to a Turing machine. > > > > But more seriously when I started asking about writing images to > > floppy disks, I asked what options were available and what I'd need. > > Apart from the (IMHO) stupid suggestion of a 1990's PC compatible, the > > only thing that was mentioned to me was the Greaseweazle. Nobody > > pointed me at web sites giving comparisons between the various methods > > and devices. > > > > -tony > >
[cctalk] Re: Getting floppy images to/from real floppy disks.
On Sun, Jun 11, 2023 at 9:07 PM Sellam Abraham via cctalk wrote: > "While I don’t recall saying that, I may well have - I know that I was > involved in the engineering question of how safe it would be to use. > > The inverter produced 230 VDC, which it turned out could be safely fed to > the 120VAC input without more than a single diode drop reverse voltage > across an electrolytic filter capacitor. This was due to the power supply’s > design having a voltage doubler as the first stage. I find that curious (read : I don't see how it could work, at least not reliably.) The power supply in the Osborne 1 and 1A is an Astec SMPSU. The input stage is the conventional one. Mains input goes through a filter circuit to a bridge rectifier. The output of the bridge rectifier goes to 2 electrolytic capacitors in series. There is a voltage selector link between one side of the AC input to the bridge rectifier and the centre tap of the capacitors. In the Osborne 1, this link is hidden on the PSU board and you have to dismantle the machine to get to it. On the 1A it's set by a little plug-in PCB in the mains input module on the back which you turn round for 115V or 230V mains. On 115V the link is in place. 2 of the diodes in the bridge and the 2 capactors form a voltage doubler circuit. Each capacitor charges to about 160V. You get 320V across the pair to feed the chopper. On 230V, the link is open. The bridge rectifier works as you might expect, the 2 capacitors get around 320V across them and charge equally (so about 160V on each). Again 320V to the chopper. Now if you feed in 230V DC with the link in the 115V position, one capacitor (only) will charge to the full 230V. That is more than the working voltage of said capacitor. The other will not charge at all from the input. Meaning the chopper circuit is fed from the charged capactior with another one in series. That one is liable to charge up with a reverse polarity due to the action of the chopper. Bang! -tony
[cctalk] Re: Getting floppy images to/from real floppy disks.
On Mon, Jun 12, 2023 at 1:25 AM Chuck Guzis via cctalk wrote: > > I'm a bit surprised that there don't seem to be any adaptations that > hook into the head pre-amps and use an ADC to give a view of what the > read signal actually looks like. Maybe that's asking too much--there > are certainly MCUs with sufficiently fast ADCs and memory to do this. I suspect that would be too drive-specific for most users. Yes the head preamp outputs are nearly always available on testpoints on the drive PCB (you use them when doing a head alignment) but having to find them and connect to them could be non-trivial. At least with the flux transition interfaces all you have to do is plug into the normal drive ribbon cable connector. -tony
[cctalk] Re: Greaseweazle part 2
> Fundamentally, it seems to me that they're all the same basic hardware, > timing intervals between flux transitions. > > So other than the soaftware, what's the difference? I could make a stupid comment and ask 'what's the difference between a PDP8, PDP11, PERQ or HP9830?'. Apart from having finite memory, all are (I believe) equivalent to a Turing machine. But more seriously when I started asking about writing images to floppy disks, I asked what options were available and what I'd need. Apart from the (IMHO) stupid suggestion of a 1990's PC compatible, the only thing that was mentioned to me was the Greaseweazle. Nobody pointed me at web sites giving comparisons between the various methods and devices. -tony
[cctalk] Greaseweazle part 2
Well, I've got the Greaseweazle software to run, but I don't know why, which is hardly encouraging. Installing various Windows updates, downloading .dlls, and puting the latter in various directories changed the error messages but it never actually worked. But downloading the latest Greaseweazle software did, it ran first time. So no idea what I was doing wrong (maybe 32 bit .vs. 64 bit Windows applications?) I can now get the list of commands when I run gw.exe. And can get help on them using the -h option. I've not tried connecting a drive yet, but the software can find and talk to the board (the green 'activity' LED turns on). For example 'gw rpm' which is used to check the drive speed by timing the index pulses times out and gives a 'no index' error which seems entrely reasonable. However I am not sure if I'll be able to use it. There is one very important thing missing : DOCUMENTATION. The 'wikii' on github is ridiculously incomplete. There is no user manual or man pages. The software source in python (a language I've never used) has very few comments and is not clear at all. It's not clear to me exactly what all the options are for, and when to use them. -tony
[cctalk] Re: Getting floppy images to/from real floppy disks.
On Wed, Jun 7, 2023 at 1:36 AM John Floren via cctalk wrote: > Thanks, Bob, that would be very helpful! I think the biggest thing is > figuring out how the pack was wired into the J4 header on the PSU... if > you've got the manuals for the DC option, it might have schematics too. Be very careful with that J4 header. It appears that the 350V DC from the power line appears there! My guess is that the battery unit contained some kind of inverter and supplied that voltage to run the machine. -tony
[cctalk] Re: First non-IBM PC-DOS Compatible PC
On Tue, Jun 6, 2023 at 7:47 PM Paul Koning via cctalk wrote: > I'm reminded of a comment about the PDP-11 family: > > "A PDP-11/xx is compatible with a PDP-11/yy if and only if xx == yy". That I suspect is actually false. The11/05 and 11/10 were the same machine, ditto the11/35 and 11/40.
[cctalk] Re: Getting floppy images to/from real floppy disks.
On Tue, Jun 6, 2023 at 3:42 AM John Floren via cctalk wrote: > It's funny that luggable power packs come up here as I'm trying to revive my > Otrona Attache... The power supply does nothing on AC input, even after a > recapping, so I thought I'd investigate the "DC Power Option" described in > the manual. Unfortunately I can't find any record that Otrona ever actually > *sold* a "DC Power Option", which would plug into an unpopulated 6-pin Molex > connector on the back of the device. Interestingly, the header inside the > power supply labeled "DC Option" is a 7-pin header, so I'm not sure which pin > was "optional" for the external connector! > > I'd just replace the power supply wholesale with a little ATX supply or > something, but the machine needs 5V, 12V, -12V, and 15V; the latter is used > to power the CRT and represents a real challenge! I've yet to find anything > that outputs all 4 levels at a reasonable price. I consider the PSU to be as much a part of the original design as any other part of the machine and like to keep them original. The schematic for the power supply is in the technical manual. It appears there's a startup supply using the mains-frequency transformer T1 as well as the SMPSU part. If that's missing then I'd suspect something around the mains input side. I assume the fuse is good! The power switch is a little odd in that it uses the triac Q1 to switch the mains, controlled by the user switch. Maybe check round that area. -tony
[cctalk] Re: Getting floppy images to/from real floppy disks.
On Sun, Jun 4, 2023 at 10:57 PM Fred Cisin via cctalk wrote: > > On Sun, 4 Jun 2023, Rick Bensene via cctalk wrote: > > an example of early "mobile computing". (Tongue firmly in cheek). > > The original Osborne 1 had a 12V power input! Actually it's +12.6V and +5.6V and you have to supply both voltages. It's one diode drop to the +5V (logic supply) and +12V (DRAM, disk motors, monitor supply), the -5V for the DRAM is produced on the logic board. I am told it was never used and that the Osborne battery pack came with an inverter to provide 110V AC. -tony
[cctalk] Re: Getting floppy images to/from real floppy disks.
On Tue, May 30, 2023 at 5:09 PM philip--- via cctalk wrote: > > I wasn't trying to solve the whole problem at once! > > A lot of people have recommended "sneakernet" to connect your modern That's an expression which always sounds odd to me. The footwear known as 'sneakers' across the Pond is, I believe, called 'trainers' here. But (a) on this list I'll use 'trainer' to refer to one of the microprocessor evaluation/learning systems and (b) I've never owned such shoes and nor do I intend to. > laptop to an older machine with drives hung off it. I was wondering > about the latter half of this - what might be the older machine with the > drives. I think that AT would be a good choice. Actually, I think the AT is not the best choice for this. I don't think the disk controller I currently have in the machine handles single density correctly. And of course it only supports 2 drives, currently 80 cylinder 5.25 and 3.5" ones. A better choice might be my TRS-80 model 4. That disk controller certainly handles single density, although it won't handle the high density data rates used on 1.2M and 1.4M PC disks and 8" floppies. It's also a Western Digital controller chip which I much prefer to Intel-esque ones.I do have a hard disk on it too -- a 3rd party unit badged 'Cumana' > > In which case we can move on to the former - what you are physically > carrying from machine to machine. > > I still think a SCSI drive is a possibility. You seem to be considering > an SD card. Some have suggested CF cards, with which I'm not familiar. > For that matter, whatever became of PCMCIA cards? How big did they get > anyway? The size shouldn't be a problem Assuming I am transfering a disk image to write to a floppy, it shouldn't be much larger than the capacity of that floppy. 1MByte should be enough. -tony
[cctalk] Re: Rainbow H7842 PSU Fault
On Tue, May 30, 2023 at 12:22 PM Adrian Godwin via cctalk wrote: > > There was an isolation transformer followed by a variac. The procedure was > to slowly bring up the variac until the control circuit was functioning, > check the waveforms around that, and then increase the supply voltage while > watching the chopper, control and output signals. This allowed the chopper > to work at low current limited by the circuit resistance and slowly > increase with supply voltage until the control circuit backed it off (which > would happen quite quickly with no output load). I don't normally use a Variac when repairing SMPSUs but I've seen diagnostic procedures in official HP (etc) service manuals which tell you to use such a device to increase the input voltage to the supply. In some cases the the control circuit is separately powered and gets the full voltage all the time, you just vary the input voltage to the chopper circuit. I would assume that an HP service manual of that vintage gave a sensible procedure for that particular design of SMPSU. -tony
[cctalk] Re: Rainbow H7842 PSU Fault
On Tue, May 30, 2023 at 11:33 AM Hans-Ulrich Hölscher via cctalk wrote: > > What can/will go wrong in either case, and why? The normally-given reason is that an SMPSU approximates to being a constant power load and draws more current if the input voltage is reduced. This can cause the chopper transistor to fail from having to handle too high a current. That said, I have run many, many SMPSUs with a light bulb in series with the mains input and had no problems at all. I run them with a minimal load (say 1A on the 5V line, so 5W power going there) and put, say, a 100W filament bulb in series with the mains. The voltage drop across the latter is <20V (I've measured it), given the local mains here is around 240V, that means the input to the SMPSU is well within the acceptable voltage range. And while the seres bulb probably won't save the chopper transistor if things go seriously wrong on the primary side of the supply, it probably will save the bridge rectifier, expensive fast-acting fuse and PCB tracks. Not to mention my nerves. -tony
[cctalk] Re: Getting floppy images to/from real floppy disks.
On Sun, May 28, 2023 at 4:36 PM Chuck Guzis via cctalk wrote: > All of these flux-transition gizmos, whether or not they're the > Applesauce, Greaseweazle, Catweasel, Fluxengine, Deviceside work > exactly the same way. A counter free-runs, and every time there's > change in direction of magnetization on a disk, the value of the counter > is sampled. The samples can be stored in memory, or send down a wire to > a host computer. The index pulse is usually included in the sample. Sure, I understand that. But as I have no experience with such microcontrollers I am happy to let somebody else write the code. As for 'all working the same way, that does not mean I don't need documentation. The commands to the controlling software could be just about anything. > Microcontrollers are the natural choice for this, but you could > implement the same in SSI TTL if push came to shove, provided that your > design had the high-frequency headroom. It's not actually all that fast, at least not compared to some things I've worked with. Pulse rates around 1MHz or so. Yes you need to sample faster than that, but it's not a ridiculous rate. I guess that's why a simple microcontroller can do it in software. > > Writing the data back is essentially an exercise in PWM. Again, a good > fit for most microcontrollers. > > All the rest, as they say, is software. > > This is not the way a conventional floppy controller operates, since > they hail from the bad old days of slower-speed logic. Much of the way > they operate is encoded as a state machine in the form of specialized > microcode. In my much younger days I disassembled and commented the microcode in the RX02. And later the microcode in the HP11305 hard disk controller (which is similar in concept). They are elegantly written bits of tight code (as they have to be) but not that hard to understand (a lot harder to write!) -tony
[cctalk] Re: Getting floppy images to/from real floppy disks.
On Sun, May 28, 2023 at 2:32 PM Adrian Godwin via cctalk wrote: > > Tony, > > An instrument slightly more to your taste than a PC might a 16500b logic > analyser. Perhaps you've already got one. I believe these can work with > both LIF and MSDOS floppies and uses an IDE HDD (which can painlessly be > replaced with CF card) in DOS format internally. I don't know if it will > handle other than 3.5" formats but it's quite possible that the support for > those formats is generic and it might work, given an appropriately mangled > hardware interface. Well, the hardware might be capable of doing other formats but it might not. Most if not all of the HP HPIB disk units are hardwired to be double density only, as is the HP4951C protocol analyser's internal disk controller and I could well believe a logic analyser would be the same. Standard PC floppy disks and all 3.5" LIF floppy disks are double density after all. In any case to handle other formats you'd have to do battle with the 16500's firmware whch I doubt is documented at that level. And I don't think schematics of the instrument exist anywhere, I believe the HP1630 was the last HP logic analyser to have schematics in the service manual (I do have one of those). If I want to do that much work I might as well make my own system from scratch. One problem with that (and a major plus-point of things like the Greaseweazle) is that traditional floppy disk controller ICs are either discontinued or at best EOL'ed. I don't like designing round parts that might not be available. -tony
[cctalk] Re: Getting floppy images to/from real floppy disks.
> I'm suprised to hear you're familliar with the GreaseWeasel but have > never heard of BlueSCSI. ( https://scsi.blue/ ). Though SASI > compatability seems "possible but not guaranteed", being an open source > project, you can probably wangle the existing PCB's/software to be SASI > compliant. More research, that i can leave you to perform, will probably > help with that endeavor. The only reason I've heard of the Greaseweazle is that it was recommended to me. I did ask at the start of this thread about other similar flux-transition interfaces but got no real information. On the grounds I could get a Greaseweazle easily, it was fairly inexpensive and it's open-source I've decided to give it a go. Still not managed to get the software working, which is probably down to the Windows installation on this machine. But I am going to take the adviceof some more knowledgeable friends before I change anything. I suspect that making a SASI-SD interface is something I could attempt myself. > Anyway, you seem to truly have your heart set on the Greaseweasel. As > long as you can write, or find, software that can turn the Weasels > output into something useful, i'm sure it will suit your purposes fine. > Of course, if you're archiving software froma truly unknown format, it > will almost definitely be the best solutions. Getting useful data into > and out of it is where the trouble will be. Most of my computers [1] use normal FM or MFM disks and I would hope the Greaseweazle software could handle that.If I can convert to/from a disk image file I can probably carry on on my own. One problem with the Greaseweazle is that there is no documentation. I would at least have expected the equivalent of a man page. Knowing what the options are, what it claims to be able to do, etc would be a good start! [1] I do have machines using GCR recording (Apple ][. Sirius (Victor 9000), etc). And M2FM (DEC RX02). And that odd double-density system used by Intel in the MDS800. But I can manage without being able to transfer to/from those, at least at the start. -tony > > Good luck! > > > Josh
[cctalk] Re: MCAS (was: Re: Getting floppy images to/from real floppy disks.)
On Sat, May 27, 2023 at 10:00 PM Alexander Schreiber via cctalk wrote: > Which is why among the more cynic^Wexperienced SREs (my line of work) > we sometimes use the term "Working As Implemented" when the code behaves > exactly as written (and ofteni as specified), but still does the wrong > thing because it (usually) was written with wrong assumptions. I generally say 'Broken as designed' meaning it does what the design says it should, but what the design specifies is stupid. I often say that about bits of the ISA bus and things designed for it, for example. -tony
[cctalk] Re: Getting floppy images to/from real floppy disks.
On Sat, May 27, 2023 at 8:47 PM philip--- via cctalk wrote: > > > > USB interfacing is hard, but SD cards are a lot simpler. So use a card > > reader thing to transfer the files to an SD card and design an > > interface for that to ISA bus. > > Thinking of that, I had actually wondered whether one could transfer the > appropriate image files from a modern PC (internet access) to a classic > PC (disk drives) using a SCSI hard drive. Not if the modern PC is a > laptop, I suppose. I suspect USB-SCSI interfaces exist but I've not looked into one. Since SCSI is a 'formatted' interface it shouldn't be too hard to make pseudo disk drive using flash memory. I must look into that to make a SASI drive for my P2000C. I suspect it's easier to use CF cards. At least some USB card readers can handle those. And the interface is essentially the same as the IDE hard disk > > Tony, I don't recall what became of the AT with 486 replacement > processor that used to be your main home machine. ISTR it had loads of > different floppy drives hung off it. Is it still functional / repairable? Still works, or at least it did when I last powered it up. But no easy way to read USB sticks or SD cards on it. -tony
[cctalk] Re: Getting floppy images to/from real floppy disks.
> Would it be possible to build a small computer, 8088/8086 > just for this? > I don't see why not, but given the choice I'd pick just about any other processor family. Probably a 68000. -tony
[cctalk] Re: Getting floppy images to/from real floppy disks.
On Thu, May 25, 2023 at 1:54 AM Mike Stein via cctalk wrote: > > I realize he's a bit eccentric, (even more so than many of us ;-) ), but I I am not 'a bit eccentric'. There is absolutely nothing mild about my eccentricities! > But it sounds like he'll explore one of the flux-transition gizmos; good > luck, Tony, and I hope you enjoy the experience! I've got a Greaseweazle V4 now. I haven't got the software working yet and I am treading carefully as an early attempt managed to mangle the drivers for my USB-RS232 cable which I depend on for a lot of work but I suspect I will get it working in the end and it will do what I need. At least it's open-source so I can read the software source code (maybe I'll have to learn Python). And I have schematics. What is odd is how many things were _not_ suggested. For example : A RPi can read files off a USB stick. Hang a floppy controller chip, possibly with buffer RAM, off the user port connector of one of those. Come up with a parallel interface between an RPi user port and ISAbus. Use that to transfer the disk images to a classic PC and go from there. It is not unheard-of for classic PCs -- even ISAbus ones -- to have 10Mbps ethernet. Most, if not all, 100Mbps ethernet ports will fall back to that. So use that to transfer the disk image. A disk image is almost certainly less than a megabyte for a classic machine, so it won't take long. USB interfacing is hard, but SD cards are a lot simpler. So use a card reader thing to transfer the files to an SD card and design an interface for that to ISA bus. CF cards are essentially the same interface as PATA (IDE) disk drives. Go from there. Just about any of those would have been easier and more likely to use bits from my junk box/computer collection than trying to get an old, but not too old, PC -tony
[cctalk] Re: ST-251 Data Recovery for Glenside Color Computer Club (GCCC)
On Wed, May 24, 2023 at 10:54 AM emanuel stiebler wrote: > > On 2023-05-24 05:26, Tony Duell via cctalk wrote: > > On Wed, May 17, 2023 at 5:29 AM Fred Cisin via cctalk > > wrote: > > > >> Last time that I tried to research it, I found that there had once been an > >> external drive in which the USB and controller werenot integrated with the > > Alas some spoilsport has removed the numbers from them. One (14 pins) > > is probably a TTL buffer to drive the disk drive signals. The other > > (still an SMD dual-in-line package but closer pin pitch than the SOIC > > of the other chip) is presumably a USB floppy controller. When I have > > time I'll probe things and see if I can figure it out. > > Some of the USB<->Floppy drives used the SMSC USB97CFDC like chips. > Which basically was an 8051, USB and a 765 FDC in a chip ... > Unfortunately the data sheets for that series say that said chips come in a 100 pin PQFP package. This things has a lot few pins and only on 2 sides of the package. So not that. -tony
[cctalk] Re: ST-251 Data Recovery for Glenside Color Computer Club (GCCC)
On Wed, May 17, 2023 at 5:29 AM Fred Cisin via cctalk wrote: > Last time that I tried to research it, I found that there had once been an > external drive in which the USB and controller werenot integrated with the > drive electronics, so that it could easily get a different drive > connected. It is, of course, not available anywhere. > I also saw a datasheet for a chip that was a USB floppy controller! It > also does not seem to be available. > I have looked in my collection and found 2 external floppy drives with USB interfaces. Both, not surprisingly, are single 3.5" 1.4M units One contains a USB floppy drive. That is, after removing the plastic casing there's a disk drive inside only. The USB cable disappears into that. After removfn the top shielding cover from that, there's a tiny PCB with an ASIC on it. USB goes to that, so do the head connections. So all in one chip, probably not hackable The other drive is more interesting. There's a drive mechanism and a little PCB hung off the back. These are connected by a tapewire type of ribbon cable, I suspect (but have NOT done any tests yet, so this is a guess) that this is the interface used on some later laptop floppy drives -- that is much the same signals as on a Shugart floppy interface. The little PCB has the USB cable soldered to it. And 2 ICs. Alas some spoilsport has removed the numbers from them. One (14 pins) is probably a TTL buffer to drive the disk drive signals. The other (still an SMD dual-in-line package but closer pin pitch than the SOIC of the other chip) is presumably a USB floppy controller. When I have time I'll probe things and see if I can figure it out. -tony
[cctalk] Re: Getting floppy images to/from real floppy disks.
On Tue, May 23, 2023 at 2:21 PM Paul Koning wrote: > > I do seriously wonder why nobody has been suggesting the > > flux-transition type of device. If it can be got to work then it would > > seem the ideal solution in that it can handle anything the disk drive > > [1] can handle, including non FM/MFM formats. > > Sure it is likely to work. But the point of the other suggestions, such as > the one I wrote saying just to use a stock floppy drive, is that it offers > another option that is easy. It would also be a particularly convenient > choice for anyone who already has such a system sitting in the closet, or can > get his hands on one easily. Given that conditional, this make a lot of sense. But the statement was originally made without the conditonal. In my first message I pointed out that I had 2 classes of computers . Classic computers which have floppy drives of various sizes but not USB ports. And this modern-ish laptop which has USB ports and no floppy drive. I think this sort-of implies I don't have an old-ish PC tucked away somewhere with USB ports and a floppy controller. > > While those flux widgets have at times tempted me, I haven't had a > requirement for one yet, and unless at some point in the future I do, chances > are I'll just stick with my existing off the shelf PC. Sure, if you've got a solution that works for you, use it. In terms of bying something now, you can get a Greaseweazle in the UK for about £25.00 including postage. I suspect that getting an old PC would cost more than that -- the hardware may be cheaper, but getting it home won't be. And I can see disadvantages to using such a machine. But other that an Apple-based solution which is not applicable to me, I've not seen any messages here on the pros and cons of the various flux transition devices. -tony
[cctalk] Re: Getting floppy images to/from real floppy disks.
On Tue, May 23, 2023 at 2:03 PM Chris Zach via cctalk wrote: > > On 5/22/2023 11:53 AM, Sellam Abraham via cctalk wrote: > > I learned a long time ago that it's a waste of time to trying to help > > someone who, instead of focusing on solutions, just comes up with endless > > reasons why your suggestions won't work. > > We used to call this "Asks for advice, argues with respondents. I have a different term for it. I call it 'being sensible' I feel it is very foolish to accept a piece of advice -- or any other information -- without questioning it. I have, alas, made that mistake too many times myself already and try to avoid doing so again. -tony
[cctalk] Re: Getting floppy images to/from real floppy disks.
On Mon, May 22, 2023 at 2:14 PM Liam Proven via cctalk wrote: > > > And > > of course it has to have the right type of disk controller, I > > certainly need to be able to handle single-density (FM) reading and > > writing correctly. Some machines can, some can't. I am hardly going to > > be able to test it before I buy it > > This is a normal ability for a machine of the 486 era, I think. Not in my experience (back in the day). I had no end of problems with friends' PCs handling single-density disks. > > > I'll go > > on public transport for things that interest me and which I actually > > want. An PC is not in that category. > > I am sorry but that is simply rude, and in context, it is adding an > insult to the prior insult. If you want the ability, get off your > backside. If you don't, then suffer in silence. Don't call people > stupid and then add "that is stupid because I can't be bothered." > I did not call you stupid. I called the suggestion stupid. Which I still consider it to be. I can be bothered. I could be bothered to design the darn thing from scratch, actually, which would probably take less time. > > > Not to mention the fact that I > > doubt I could carry the system box, monitor and keyboard in one go. > > Why would you have to? Who said you did? Nobody. You made this up, > then called me stupid for words you put in my mouth. > My experience is that most sellers, if selling a complete system, want the whole lot gone in one go. They do not want multiple visits to pick it up a bit at a time. And if the machine is not near me then fares quickly mount up if you have to make several trips. One other point I forgot is the size of such a machine. I don't have space for one. My house is not large and it's filled with things that interest me -- like classic computers, tools, electronic test gear, books, etc. > > Having it sent to me is inconvenient > > Nonsense. The bulk of commerce these days is mail order because it is > *more* convenient. Obviously you know my life better than I do. Having parcels delivered is inconvenient. I do have things to do that require me to be out of the house at certain times. I can't be in at a particular time necessarily. And many of the jobs I do can't be stopped because the doorbell rings. You try assembling a mechanism with tiny parts, many spring-loaded, and having to stop mid-way. It doesn't work. Don't tell me that the delivery company will give the time/date the parcel will be delivered. Such information is totally inaccurate in my experience. -tony
[cctalk] Re: Getting floppy images to/from real floppy disks.
On Mon, May 22, 2023 at 5:25 PM j...@cimmeri.com wrote: > > On 5/22/2023 5:38 AM, Tony Duell via cctalk wrote: > >>> I hereby formally retract my erroneous suggestion of a "386 98,SP2 desktop > >>> with floppies and USB", and replace my suggestion with: > >>> "a PC with USB and floppies", and let Tony decide what vintage to use. > >> Fully concur. If it were me, I'd probably suggest some box with from > >> the end of the era which came with an onboard floppy controller, and > >> dual-boot 98SE and some old Linux that can handle such a thing, like > >> Slackware or Debian. That would cover the most bases. > > I am sorry, but I think this is a stupid suggestion for many reasons. > > > It is, however, a viable suggestion, and that is better than none :) I do seriously wonder why nobody has been suggesting the flux-transition type of device. If it can be got to work then it would seem the ideal solution in that it can handle anything the disk drive [1] can handle, including non FM/MFM formats. Is it that such devices don't work, or what? The Greaseweazle has schematics, firmware source and application source all available (OK I don't know python but would be happy to spend time learning that if need be) and thus would seem to be easier to keep going than some unknown PC. [1] Actually, do any such devices handle hard-sector disks? There seems to be no technical reason why not, but I've never seen it listed as a capability. But as just about all my machines use soft-sectored disks this is not really an issue. [...] > I wouldn't worry about the built in disk controller. You can add the > functionality you need with an Adaptec SCSI controller w/ floppy. Which AFAIK is no longer made and not necessarily available. > > Why do you need a monitor and keyboard?And since you don't drive, > again, have you heard of eBay? Well,, I need a monitor so I can see I've typed the command correctly, use a GUI (if that's what the OS uses) and see error messages. I need a keyboard to type the commands, and indeed to satisfy the POST of most such machines. I do not have such things around. Very few of my computers are PCs. -tony
[cctalk] Re: Getting floppy images to/from real floppy disks.
On Sat, May 20, 2023 at 12:22 PM Liam Proven via cctalk
wrote:
>
> On Fri, 19 May 2023 at 23:40, Fred Cisin via cctalk
> wrote:
> >
> > On Fri, 19 May 2023, Liam Proven via cctalk wrote:
> > > I do remember that, because I carried around a USB key with an
> >
> > Thanks, everybody for the reminders of the Windoze history.
>
> ;-)
> >
> > I hereby formally retract my erroneous suggestion of a "386 98,SP2 desktop
> > with floppies and USB",
> > and replace my suggestion with:
> > "a PC with USB and floppies", and let Tony decide what vintage to use.
>
> Fully concur. If it were me, I'd probably suggest some box with from
> the end of the era which came with an onboard floppy controller, and
> dual-boot 98SE and some old Linux that can handle such a thing, like
> Slackware or Debian. That would cover the most bases.
>
I am sorry, but I think this is a stupid suggestion for many reasons.
The first problem is finding such a machine in known-working
condition. Second-hand computer shops are few and far between and
generally don't trade in machines that old. Similarly pawnbrokers
('Cash Converters' and the like) don't deal in them. I am not sure I
would want to trust something from an unknown seller on the web. And
of course it has to have the right type of disk controller, I
certainly need to be able to handle single-density (FM) reading and
writing correctly. Some machines can, some can't. I am hardly going to
be able to test it before I buy it
Next there's the problem of me getting it home. I don't drive. I'll go
on public transport for things that interest me and which I actually
want. An PC is not in that category. Not to mention the fact that I
doubt I could carry the system box, monitor and keyboard in one go.
Having it sent to me is inconvenient and I am not sure the machine
would survive. Not to mention it would cost more than the machine is
worth.
Then there's the problem of keeping it going. It's not a PERQ :-) I
realise that spare ICs always were unobtainium. But replacement
modules -- disk drives, motherboards, etc are no longer made or easily
available. I have no PCI cards in my collection at all. No ATX power
supplies. I might be able to find a VGA monitor but that's pushing it.
And of course no documentation. At least the Greaseweazle is
open-source which is better than nothing.
And drives. It was suggested that I get a double 5.25"/3.5" drive.
Err, no. The 5.25" is going to be 80 cylinder (to handle 1.2M disks)
which means writing to 40 cylinder disks is a bad idea.
And I am not sure the software exists to do what I want on such a
machine. I don't want to have to write it myself!
-tony
[cctalk] Re: ST-251 Data Recovery for Glenside Color Computer Club (GCCC)
On Thu, May 18, 2023 at 8:03 PM Fred Cisin via cctalk wrote: > > > > > On Thu, 18 May 2023, Robert Feldman via cctalk wrote: > > Can you fix it using MODE.com from a DOS prompt? > > Or, a full re-install of the USB-RS232 dongle? Depends on what you mean by a re-install... Asking Windows to check the driver and install the correct/latest one did not help. Deleting the driver totally and then removing/reconnecting the USB end of the interface cable got it to find the correct driver. So at least I can talk to my device programmers, etc, again. Quite why the software decided to replace that driver for me without telling me is a mystery. Needless to say I am not going to run it again. > > Long ago, I learned, the hard way, that I should always make a complete > backup, or at least a restore point, before installing anything new, or > making any change. > > I wish that I would remember to apply that lesson more consistently. 'Scratch monkeys' sprng to mind :-) -tony
[cctalk] Re: ST-251 Data Recovery for Glenside Color Computer Club (GCCC)
On Thu, May 18, 2023 at 5:28 PM Mike Katz wrote: > > I run the greaseweazle under window 10 and windows 11. I havent' seen > any problems as of yet but I am using the command line utilities mostly. I was running from the command line too. Typing 'gw' just gets a dialogue box moaning that the program can't run because I don't have some .dll or other. But that's a minor issue. The loss of RS232 communications is a lot more serious. -tony
[cctalk] Re: ST-251 Data Recovery for Glenside Color Computer Club (GCCC)
On Thu, May 18, 2023 at 5:05 PM Chuck Guzis via cctalk wrote: > > On 5/18/23 08:48, Tony Duell via cctalk wrote: > > > I wish I'd never listened to people who said this was easy and would work > > fine. > > > > Never again. > > > > I warned you about modern open-source, didn't I? Indeed you did. I should have listened to you. > I'm surprised that nobody suggested the Catweasel line. Probably one of > the first, if not the first, transition recorder generally available. > Ranges from the Mark I, which is an ISA device to the Mark 4, which is > PCI. Long out of production--I suspect that Jens decided that he had to > move on. Problem is that I have no ISA machines with a USB port. And nothing at all with PCI slots. > > Software for that was always open-source, yet nobody seems to remember it. > > I suspect that greasweazle appeals because it's cheap. There's also > Kyroflux, DeviceSide, FluxEngine...using MCU based designs. I am not going to try any of them. I just hope I can find some way to restore RS232 communications on this machine. As it is, I can neither do real work nor hobbies. > > The idea's the same. What I'm a bit surprised about is that there has > been no emulation of a generic floppy controller offered. It can't be > that complex; if I recall correctly the NEC 765 only used 1100 words of > microcode. I know the microcode for the DEC RX01 (FM only) which was published in the printset and the RX02 (FM and M2FM) which was never published but which I disassembled and commented were not hard to understand. -tony
[cctalk] Re: ST-251 Data Recovery for Glenside Color Computer Club (GCCC)
On Thu, May 18, 2023 at 3:16 PM Antonio Carlini via cctalk wrote: > At ~£25 you're unlikely to lose much with either of the two front > runners :-) Unfortunately in my case that is not true. I ordered a Greaseweazle earlier today and downloaded the software. Of course there is no such thing as documentation I read on the web site that to use it under Windows 8.1 I had to install a device driver and to do that I needed a program called 'zadig.exe'. I downloaded that following the link on the Greaseweazle page. Now I don't yet have the Greaseweazle but I decided to just check that the programs would run. They do not The gw software itself falls over with a moan about a missing .dll. The bit I recognise is 'stdio'. No idea where or how to get htat. zadig was worse. I gave it permission to make changes but AFAIK didn't ask it to change anything. None-the-less I've lost RS232 communications (the USB-serial cable was plugged in at the time). I can find no way to get that to work again. So I've lost the ability to program and read PALs and EPROMs. talk to my palmtops, calcultors and other machines and so on. Bascially I can't do much.. I wish I'd never listened to people who said this was easy and would work fine. Never again. -tony
[cctalk] Re: ST-251 Data Recovery for Glenside Color Computer Club (GCCC)
On Wed, May 17, 2023 at 9:28 PM Mike Katz via cctalk wrote: > > I have to agree with the folk on here who recommend some kind of flux > reader/writer like the greaseweazle. OK, that's what I thought. Now what are the options. Greaseweazle or ? What are the advantages and disadvantates of each? For the Greaseweazle it looks like I can get one and it seems to be open source with schematics of the hardware. I'd prefer more buffering of the disk drive signals, but anyway. Will it do what I want? -tony
[cctalk] Re: ST-251 Data Recovery for Glenside Color Computer Club (GCCC)
On Wed, May 17, 2023 at 8:49 PM Chuck Guzis via cctalk wrote: > As much as Tony doesn't like it, I need to point out that a modern MCU > quite often has as much (or more) RAM, and runs faster than many older > PCs. Consider, for example, the lowly STM32H7A3 series. 1.4MB of RAM, > 2MB of program flash, 5 DMA controllers, ethernet, TFT LCD, up to 164 5V > tolerant GPIOs, USB OTG...I won't go on. Now wait a second. I never said that in this thread. I said that I know nothing about them. I am NOT, repeat NOT, contemplating wiring up a load of TTL or AM2900 bit slice chips or... to make a floppy controller or a flux transition time recorder. I am happy to use a microcontroller. But as I know nothing about them I am looking for a solution that 'works'. I do not want to start having to rewrite the firmware. > > Why tinker around with a PC when your MCU is more powerful? I store my > retrieved data on a 32GB SD card. I enjoy classic computers which are simple enough for me to understand and to get to do what _I_ want. This does not mean they're the only thing I consider for solving a problem. -tony
[cctalk] Re: ST-251 Data Recovery for Glenside Color Computer Club (GCCC)
On Wed, May 17, 2023 at 8:38 PM Fred Cisin via cctalk wrote: > The earliest Osbornes were single density with ten 256 byte sectors per > track. I was able to write some code on TRS80 model 1 to read those. > Many PC FDCs, including the IBM 5150/5160, can not do FM/single-density. > > Then Osborne came out with a "double density upgrade". The > MFM/Double-density Osborne disks are easy to do with PC, if you are > familiar with INT13h and INT1Eh. It's odd... The Osborne had a double-density-capable disk controller chip (WD1793) from the start. The double density board is the necessary data separator and write precompensation stuff. I have it in my Osborne, thankfully. I also have the 80 column 'Screenpac' upgrade, which is not relevant here. -tony
[cctalk] Re: ST-251 Data Recovery for Glenside Color Computer Club (GCCC)
On Wed, May 17, 2023 at 5:54 AM Chuck Guzis via cctalk wrote: > > On 5/16/23 21:29, Fred Cisin via cctalk wrote: > > >> From what I've heard, there has been substantial progress on the flux > > transition devices, with decoding the track to sectors, and even support > > of some file systems! > > > > For years I have been telling the community that flux transition is > easy-peasy on modern MCUs. You have fast timers, "capture mode" and > even DMA for the capture process. [..] > It's not hard! It's not hard if you know about modern microcontrollers, know how to program them, know how to handle the USB interface back to the modern machine, know how to write programs on said modern machine to talk to the microcontroller over the USB interface and so on. I know NONE of that. It's not hard to rebuild a floppy drive and align it from scratch. It's not hard to understand the microcode in an HP9830 and its HP11305 disk control. It's not hard to replace heads in an RK05. It's not hard to wire up a processor from a pile of TTL chps. It's not hard to make an interface between a Trend HSR500P tape reader and a TRS-80 CoCo. It's not hard to rebullt a rotary telephone dial. it's not hard to repair a spring-driven chiming/striking clock. It's not hard to... I've done them all over the years. This does not mean I can design and build a flux-transition type of floppy disk reader/writer. Actually I probaably could if I had to but I understand such devices already exist so I'd rather use a known design if there is a recomended one, one that people have experience of. -tony
[cctalk] Re: ST-251 Data Recovery for Glenside Color Computer Club (GCCC)
On Wed, May 17, 2023 at 5:29 AM Fred Cisin via cctalk wrote: > > >> Similarly, he could buy a cheap external USB 3.5" drive. Write content to > >> that drive on the modern machine, and read those floppies on the older > >> machines. The readily avaailable one have firmware that only supports > >> 720K, 1.4M, and [sometimes] NEC-style "mode 3". > > On Wed, 17 May 2023, Tony Duell wrote: > > I have one but AFAIK it only supports 1.4M. A format that few of my > > other machines support. > > Have they stopped making ones that include 720K? I've never found one that claims to support 720K. OK, OK... When I have a little (?) spare time I'll pull my USB floppy drive to bits and try to work out just what the hardware consists of. > That's something that almost all of your MFM machines could be coerced > into handling. > > >> I get the implication that he is considering USB flux-transition devices > >> that could be coerced into acting as a general purpose floppy controller. > > I am not adequately familiar with them. Nor am I,which is why I am asking about them. I've heard they are a possible solution to my problems. I would like to know more, which ones exist, which are recomended (the Greaseweazel, the only one that has been seriously suggested to me, is at least open source and has schematics available), what they will do, etc And to jump to a later point you make, I want to know just what software tools exist to deal with the flux-transition file (if that's the term). For example for an FM or MFM disk image, are there tools to convert between a .IMD file and said flux transition file, between a .TD0 file and said flux transition file, etc. And what software tools exist to work on disk images. If I have a .IMD file of a CP/M disk, say, can I add a file to it, for example? -tony
[cctalk] Re: ST-251 Data Recovery for Glenside Color Computer Club (GCCC)
On Tue, May 16, 2023 at 11:42 PM Fred Cisin via cctalk wrote: > > On Tue, 16 May 2023, Wayne S via cctalk wrote: > > Tony in response to your original idea of wanting to download images for > > use on you existing machines ( did i get that right?), i think you have Yes. I've got the machines running, I see software for them on websites (including bitsavers), I want to use it. > > everything you need already. Download the images to your win 8 box then > > use file transfer software (kermit or xmodem) to serially transfer to > > the specific box you want to use the software on and the use the floppy > > on that box to write the floppies. It seems like there is a version of > > kermit made for every box imaginable. The only possible gotcha is does > > the box have a serial port. > > He would have to add a serial port (USB to serial dongle). That was the first thing I bought for this machine. And Kermit was one of the first things I installed. Last time I used it was yesterday to transfer an EPROM dump file from my HP95LX... But I really would like to get a more direct solution. As for the target machine having a serial port, one of the machines I want to get stuff onto is an Osborne 1A. The serial port on that is horrible. The baud rate generator divides down the master clock to get 19200Hz. That's fed to the serial chip which, amazingly for a Z80 machine, is a 6850. You can program that to divide by 16 (for 1200 baud) or divide by 64 (for 300 baud). That's it. OK, there's a jumper on the mainboard to double those rates, and a cut-n-wire modification in the technical manual for 9600 and 2400 baud, but > > Although, . . . > many years ago, in the early days of USB, there was a cable and software > provision for transferring files USB yo USB. 'course, it's doubtful that > any of his other machines have USB. If my other machines had USB I'd just put the files on a memory stick. > > > Similarly, he could buy a cheap external USB 3.5" drive. Write content to > that drive on the modern machine, and read those floppies on the older > machines. The readily avaailable one have firmware that only supports > 720K, 1.4M, and [sometimes] NEC-style "mode 3". I have one but AFAIK it only supports 1.4M. A format that few of my other machines support. > I get the implication that he is considering USB flux-transition devices > that could be coerced into acting as a general purpose floppy controller. EXACTLY! I was told that was the best solution for this sort of thing. Are there any downsides to doing it that way? If I do go that route, what are the options? I have no knowledge of them and thus no preference for one over another As I said at the start I am clueless about this. I really need somebody to talk me through it, what to get, what to build, what to download etc. -tony
[cctalk] Getting floppy images to/from real floppy disks.
As you know I've recently restored a couple of CP/M luggable computers. I also have many other machines with floppy disk drives, 3", 3.5", 5.25" and 8" The machine I connect to the internet with is a more modern laptop runnng Windows 8.1. Essentially its only interfaces are USB ports. I would like to be able to : Download disk images (I assume in .IMD or .TD0 format) and write them to real floppy disks to use in my old machnes If possble, for the more common filesystems like MS-DOS or CP/M, be able to work with these images on the modern PC at the file level. For example, if I download a CP/M progam as a .COM file I'd like to be able to put it into a disk image of a Philips P2000C disk, then transfer that image to a real floppy and put it in a drive on the Philips machine. I understand there are designed based on a modern microcontroller that connecct to a USB port and a disk drive. Software on the PC translates between the disk image and the accurately-timed pulses corresponding to flux transitions on the disk. This unit links to a real disk drive, you run the software and it reads/writes a real disk in said disk drive. Now... I can handle a 'scope. I can handle a logic analyser. I can handle a soldering iron. I can handle an engineer's lathe. I can rebuld and align floppy disk drives. I can program most 8-bit micros along with PERQ microcode, PDP11 mahine code, etc BUT I don't have a clue when it comes to modern PCs, modern microcontrollers or USB ports. So what I am asking is for people to describe what to do as in : Buy this microcontroller board Buy this blank PCB and solder the components given in the BOM to it. Download this software and install it by doing this. Connect a standard floppy drive to this connector Run the software, specify the disk image file and sit back. -tony
[cctalk] Re: Current Loop Schematics
On Tue, May 2, 2023 at 1:34 PM Paul Koning via cctalk wrote: > > It seems surprisingly hard to find that, though this > https://forum.vcfed.org/index.php?threads/rs-232-to-current-loop-interface.47841/ > is close. > > Conceptually it's really easy. The main tricky part, certainly if you're > driving a mechanical terminal like a Teletype, is the current source. You > need something that can drive 20 mA into an inductive load. The classic > answer was to use a fairly high voltage with a big series resistor so the > inductive impedance is much less than the resistance. A current regulator > would be a modern replacement. Also, for the case of the inductive load, > you'd need a shunt diode across the switch to absorb the voltage spike from > the inductor when the current is switched off, otherwise the switching > transistor will be quickly destroyed. The common version of the Model 33 Teletype with a current loop interface [1] has a bit of electronics inside. A little driver PCB with a couple of transistors on it, a power transformer for it and so on. The result is that although the interface is 20mA or 60mA current loop you are not driving the receive magnet directly and there are no high voltage spikes at the interface terminals. [1] This is by far the most common version of the Model 33 in the UK. If you do have to drive the solenoid directly then (as you're in the UK) look out for the RSGB [2] Teleprinter Handbook. Although, not surprisingly, this is biased towards amateur radio RTTY operation, it has a lot of information on mechanical teleprinters, how to drive them (with circuit diagrams) and so on. [2] Radio Society of Great Britain. Basically our equivalent of the ARRL. -tony
[cctalk] Re: Schematics for Lear Siegler ADM31?
On Tue, Apr 18, 2023 at 11:04 PM John Robertson via cctalk wrote: > > I like to start with schematics before poking too much... So do I. > > I assume bad caps (will replace with low-ESR high temp), and possibly > blown transistor(s)... > > *And Gregory Beat sent me a link that covers the 1001 SMPS very neatly:* > > http://www.bitsavers.org/pdf/boschert/Boschert_OL25_Single-Stage_Power_Supply_Maintenance_Manual_May79.pdf > > and it was buried on bitsavers - where I went before bothering the list! That is clearly not one of the '2 stage' ones that fail in spectacular ways. It's a relatively conventional SMPSU and shouldn't be too hard to sort out. -tony > > Thanks folks! > > John :-#)# > > > > > > > > >> On Tue, Apr 18, 2023 at 12:20 AM John Robertson via cctalk < > >> cctalk@classiccmp.org> wrote: > >> > >>> I've checked bitsavers.org (Al does a great job!), and a number of > >>> forums, but no luck finding schematics for my ADM31 that I am trying to > >>> resurrect. The power supply has issues and I need to identify a blown > >>> out resistor - the switching supply is a Boschert model 1001 date code > >>> 7943 Revision J. > >>> > >>> John :-#)# > >>> > >>> -- > >>> John's Jukes Ltd. > >>> 7 - 3979 Marine Way, Burnaby, BC, Canada V5J 5E3 > >>> Call (604)872-5757 (Pinballs, Jukes, Video Games) > >>> flippers.com > >>> "Old pinballers never die, they just flip out" > >>> > >>> > > -- >John's Jukes Ltd. > 7 - 3979 Marine Way, Burnaby, BC, Canada V5J 5E3 > Call (604)872-5757 (Pinballs, Jukes, Video Games) >flippers.com >"Old pinballers never die, they just flip out" >
[cctalk] Re: Schematics for Lear Siegler ADM31?
On Wed, Apr 19, 2023 at 2:37 AM Tom Hunter via cctalk wrote: > > ... or four $20 power transistors to protect a 10 cent fuse like on the DEC > VR-14 display. In general the transistor(s) will fail short-circuit, thus taking out the fuse too. Some switch-mode power supplies use special fast-acting fuses which can actually be more expensive than the chopper transistor. -tony
[cctalk] Re: Schematics for Lear Siegler ADM31?
On Tue, Apr 18, 2023 at 2:51 PM Tom Hunter via cctalk wrote: > > The blown out resistor likely has "blown out" for a reason. > The replacement will probably suffer the same faith unless you find the > root cause. As soon as I saw 'Boschert' mental alarm bells triggered Boschert made a particularly unfriendly (to the repairer) type of SMPSU which I call the '2 stage'. I can explain how it works if necessary, but be warned that with one of those if a particular power transistor fails (and it often does), it takes out a couple of other power transistors, the current sense resistor, numerous small transistors, the regulator chip, the fuse and sometime PCB tracks. They're not all like that, but I will agree that a burnt-out resistor in an SMPSU nearly always means other components have failed. It's likely the same PSU was used in other devices, you might want to look through all the service manuals you can find to see if it turns up. Can you make a photo of the PSU available somewhere in case somebody recognises it. -tony > > On Tue, Apr 18, 2023 at 12:20 AM John Robertson via cctalk < > cctalk@classiccmp.org> wrote: > > > I've checked bitsavers.org (Al does a great job!), and a number of > > forums, but no luck finding schematics for my ADM31 that I am trying to > > resurrect. The power supply has issues and I need to identify a blown > > out resistor - the switching supply is a Boschert model 1001 date code > > 7943 Revision J. > > > > John :-#)# > > > > -- > > John's Jukes Ltd. > > 7 - 3979 Marine Way, Burnaby, BC, Canada V5J 5E3 > > Call (604)872-5757 (Pinballs, Jukes, Video Games) > > flippers.com > > "Old pinballers never die, they just flip out" > > > >
[cctalk] Re: Speaking of tapes....
On Wed, Mar 8, 2023 at 3:11 AM Chris Zach via cctalk wrote: > > I noticed in a Dectape 2 document that the tape drives are just DC100 > models. Are there any specific documents on what kinds of signals should > be coming out or into them? > > I'd like to fix this TU58. The drive unit from a TU58 is just the head, motor, tacho sensor and a couple of microswitches. It contains no electronics at all (unless you count the LED and phototransistor in the tacho sensor). All the electronics to handle the signals from those is on the controller board. This consists of a simple 8085-based system (IIRC, 8085 processor, 8155 RAM/IO, ROM, serial interface, etc) and the analogue read amplifier etc. -tony
[cctalk] Re: Research machines RM 380
On Mon, Feb 27, 2023 at 10:29 AM jake utley via cctalk wrote: > > I’ve been restoring a RM380 I picked up not long ago and it’s been good news > and bad news. All the cards are in wonderful condition and the case is > presentable however the two BASF 6106 floppy drives are highly corroded and > probably won’t work again but this isn’t what I’m wondering, the original > supply is a little rough but looks tone perfectly restorable with the > exception of the key lock been stuck (problem to solve later) and I can get > all the parts needed to replace the three filters but it is a 70s linear > supply and if my s-100 experience has told me anything they might not be the > most reliable. What would you all recommend restoring it and keeping it > original or fitting some modern SMPS in its place. It is a low serial number > as well (691) but saying I want it to be reliable I’m torn. I would certanly recomend keeping it original. My experience is that a linear supply, although less efficient than a switch mode one, is a lot more reliable. There's a joke about the crazy PSU in the Zenith ZVM1220 MDA monitor thst said unit combines 'The reliability of a switcher with the efficiency of a linear'. It's also a lot easier to fix a linear supply than a switcher and there are not high voltages on any of the semiconductors. Getting back to the 380Z, there's a schematic of one version in the service manuall. But even if it doesn't agree, you can trace out a schematic in under an hour and that's going slowly. It is a very simple unit using normal 3-terminal regulators in the standard way. I'd 'megger' the transformer just to be safe as the machine seems to have been stored in poor conditions. Then power it up with a 'lamp limiter' on the mains input and no load on the output (unplug the cables from the driives and the 1 or 2 10-way ribbon cables from the PCBs). Most likely it will be fine, even with the original smoothing capacitors. -tony
[cctalk] Re: Nuking an MFM drive with a magnet, format/servo gone?
On Sun, Feb 5, 2023 at 11:12 AM emanuel stiebler via cctalk wrote: > Keep "all" magnets away from disks :) The hubs of 3.5" floppy disks and of the disk packs used in RK05s, RL01s/02s, RK07s, etc are locked to the spindle by a ring magnet. -tony
[cctalk] Re: Nuking an MFM drive with a magnet, format/servo gone?
On Fri, Feb 3, 2023 at 5:21 PM Alexandre Souza wrote: > > I thoug the right one was st512...can you enlighten me on this subject Tony? I've never heard it called that. It's often called 'ST506' but that drive had a few differences from the later ones. it didn't support buffered seeks AFAIK. The ST412 did and was the most common of a family of 3 similar drives (ST406, ST412, ST419) so it tends to be used as the de-facto name of the interface. -tony
[cctalk] Re: Nuking an MFM drive with a magnet, format/servo gone?
On Fri, Feb 3, 2023 at 4:57 PM Chris Zach via cctalk wrote: > Yep, with 15 yeads it had a servo platter that is gone. Oh well, it's > securely erased :-) I'll toss the drive, keep the electronics interface > and keep it in mind for the future. If you have the tools, it's worth carefully dismantling the dead HDA taking photos as you go and keeping parts like the heads and flexiprint. Other bits like the positioner magnet and spinde motor mght be worth keeping too. Some months ago I was working on a Toshiba hard drive in a Stride 440 and I wish I'd had some idea of what was on the flexiprint between the logic board connector and the heads. Of course without a clean room I didn't dare open the HDA, but had a defective or dismantled one been available I'd have paid reasonable money for it. -tony
[cctalk] Re: Nuking an MFM drive with a magnet, format/servo gone?
On Fri, Feb 3, 2023 at 4:40 PM Chris Zach via cctalk wrote: > > Question: I just used a strong magnet to wipe an old Maxtor MFM drive > (magnet on outside of case). Now the drive will not even seek properly > on start up, just endlessly moves the heads.. > > Is the drive now toast? Do MFM drives have embedded servo information on > the platter formatted by the factory? I assume by 'MFM' you mean a drive with an interface similar to the ST412. Embedded servo is rare (unheard-of) on ST412 interfaced drives simply because the manufacturer has no idea how it will be low-level formatted and thus where the sector headers will be. So no safe place for the servo bursts on the data surfaces But a dedicated servo surface is very common on larger such drives. That's why you often see an odd number of data heads. There is a head on each side of each disk, but one is used for the servo. Sounds like you've wiped that. No sensible way to recover I'm afraid -tony
[cctalk] Re: Computer Museum uses GreaseWeazle to help exonerate Maryland Man
On Fri, Feb 3, 2023 at 2:41 PM Will Cooke via cctalk wrote: > Yes. The thresholds shift with temperature. Some companines (DEC?) used > temperature-compensated amplifiers to address the issue. IBM, on some models > like the 1620, kept the cores at a constant (elevated) temperature. Most of the core memories that I've worked on, including quite small ones like the HP9100B, have a thermistor physically next to the core array to control the threshold. I also seem to remember there were MAINDECs for various PDP8 and PDP!1 core units that did the worst case sequence for heating the cores and checked the memory was sill operational. -tony
[cctalk] Re: 5150 cassette (Was: DLOAD BASIC command for Color Comp
On Tue, Jan 31, 2023 at 11:50 PM Ali via cctalk wrote: > > > (~$300), monitor (CGA had compoosite output, so could connect to cheap > > CCTV, etc. monitors, and CGA even had a dedicated 4 pin Berg for the > > SupRMod RF adapter), and maybe serial, and/or parallel. > > Fred, > > This is the first time I am hearing about this. I always thought the > connector was for light pen input. No, that's the 6 pin Berg alongside it. IIRC the MDA card had the light pen connector too, but it was never documented or supported as the long persistence of the 5151 monitor meant that a light pen wouldn't work with it. -tony
[cctalk] Re: DLOAD BASIC command for Color Computer 1/2 heritage
On Tue, Jan 31, 2023 at 6:53 PM Jim Brain via cctalk wrote: > I think (I might have mentioned it at the thread start) it was part of a > plan for a school network. Tandy offered a similar setup for schools > for the Model 1/3/4 systems, where the "host" could send programs, and > the clients would load from the common host system. IIRC there was the Network 1 which was 500 baud M1/3/4 only, and the Network 2 which was very similar but could also handle 1500 baud M3/4 and Coco (and M100?). These used the casstte ports and allowed the host machine to 'broadcast' a file (program) to all the student stations or load a file from one student station at a time back to the host. If there had been a version using DLOAD then presumably it would have been host to student stations only, so the teacher couldn't save/print/examine a student's work. There was the Network 3 which used RS232 ports on the M3 (and M4?) but which required a ROM change in the student stations I think. -tony
[cctalk] Re: DLOAD BASIC command for Color Computer 1/2 heritage
> "DLOAD is the most obscure command in the Color > Computer and absorbs a substantial amount of space in the ROM. DLOAD is so > poorly > understood because Tandy has never made the necessary companion routine, > DSEND. I wonder if it was originally intended (or even used) at the factory to download a diagnostic program into the machine for final testing, or for similar use at repair centres? The IBM5150 has a similarly obscure facility to download a diagnostic program through the keyboard port (this one is sort-of documented in the BIOS sources) -tony
[cctalk] Re: DLOAD BASIC command for Color Computer 1/2 heritage
On Tue, Jan 31, 2023 at 10:56 AM Philip Belben via cctalk wrote: > > > ZX80, ZX81, Spectrum, Acorn Acom, Acorn Electron, BBC Micro, etc, etc. > > Do you count machines like the Amstrad CPC464 which had a built-in > > cassette recorder? > > And don't forget the Commodore cassette port - used on the PET, VIC, > C64, ... I think somebody else mentioned that one. > > This blurred the line between built-in cassette drives and cassette > ports, since the built-in drive on early PETs became the separate drive > on later ones, plugging into the same port. > > This didn't just switch the motor, it powered it from the computer. When I got my first PET, I didn't have the Commodore casstte recorder for it. So I designed a simple interface to link a normal cassette recorder to the PET's edge connector. I used the motor drive line to operate a relay with the contacts going to the remote socket on the cassette unit. Since the cassette recorder I was using (a Radio Shack CCR-82) had the +ve battery line going to the internal on-off switch, then to the remote socket, then to the motor, I could sense the voltage on the appropriate side of the remote socket to indicate when the 'Play' key was pressed and use that to switch a transistor connected to the PET's cassette switch pin. > > Also unusual, I think, was that it didn't use a modem chip to generate > tones, but bit-banged them in software. Almost all 8-bit home micros bit-banged the tones, and also decoded them in software. I think the BBC micro (and Electron?) was the common exception in the UK. -tony
[cctalk] Re: 5150 cassette (Was: DLOAD BASIC command for Color Comp
On Mon, Jan 30, 2023 at 6:47 PM Fred Cisin via cctalk wrote: > The 5150 had a cassette port! > Diagnostics were supplied on cassette tape. [...] > There was an outfit that marketed a sorta network using the 5150 cassette > port, for classroom distribution, etc. There was the Radio Shack Network 2 which worked like that. It was originally designed for use with TRS-80s (a master disk system used by the teacher and diskless machines used by the students). I've never heard of it being used with the 5150 but I suspect it would work. I did hear of people using the motor control relay on the 5150 (you could control it easily from Microsoft BASIC, for example) as a single-bit output to key a CW radio transmitter (morse code), etc. And I think I read of somebody who used a 5150 as a sales cash register and used the relay to release the cash drawer. -tony
[cctalk] Re: DLOAD BASIC command for Color Computer 1/2 heritage
On Mon, Jan 30, 2023 at 5:34 PM Jim Brain via cctalk wrote: > > On 1/30/2023 11:14 AM, Chris via cctalk wrote: > > It had a dedicated cassette port? Don't most cassette ports resemble a > > serial port, or is my wonky brain making that up? What protocols did most > > cassette ports use (c64/128?, IBM 5150, coco ...)? > > Lots of systems had dedicated cassette ports, but yes, CoCo has a > dedicated cassette port, as does all the 8 bit CBM machines, I think the > Model 1/3/4 also, and doesn't the Apple II have one as well. Yes, all those have dedicated cassette ports. > I am sure > I am forgetting a bunch. ZX80, ZX81, Spectrum, Acorn Acom, Acorn Electron, BBC Micro, etc, etc. Do you count machines like the Amstrad CPC464 which had a built-in cassette recorder? > > I think it would have been hard to have the cassette use the serial > port, because cassette needs audio tones, not RS232 levels. There was an almghty kludge in the TRS-80 Modem 1. You could flip a switch and the modem serial input changed from RS232 levels to cassette levels. The modem serial output became a keyed (by the serial data) audio tone. This meant you could link it to a Model 1 cassette port and drive it with special software. It's documented in the service manual for said modem. -tony
[cctalk] Re: Computer Museum uses GreaseWeazle to help exonerate Maryland Man
On Fri, Jan 27, 2023 at 11:53 AM Chris via cctalk wrote: > C: there never was a person worse at sports then me. You have not met me! If I manage to kick or throw a ball, it will go about +/- 1 radian of where I would like it to go. I can run 100m in about 10 minutes. Get the idea? I''ll stick to getting my exercise by putting minicomputers into racks and carrying so-called portable computers on public transport. The only 'exercisers' in use here are the ones for disk drives and the like. -tony
[cctalk] Re: Computer Museum uses GreaseWeazle to help exonerate Maryland Man
On Fri, Jan 27, 2023 at 4:15 AM Fred Cisin via cctalk wrote: > > We also probably don't have very many athletes here. Not unless you class 'electronics' as a sport. I managed to do so at school many years ago, meaning that while other boys were chassis spheres and prolate spheroids about I was soldering up a Z80-based computer, experimenting with vacuum systems, teaching myself how to use machine tools and other useful stuff. -tony
[cctalk] Re: Philips P2000C restoration
On Wed, Jan 25, 2023 at 11:35 AM Adrian Godwin wrote: > > On Wed, Jan 25, 2023 at 10:27 AM Tony Duell via cctalk > wrote: >> >> >> I've put a few photos of the machine (in bits) in my flickr account here : >> >> https://www.flickr.com/photos/tony_duell/albums/72177720304931970 >> >> > > Nice ! Very thorough cleaning of the disc drive ! Don't try that unless you have an alignment disk and know how to use it! > But I'm curious about the eye-bolts. I assume not original. Do you hang it > from the ceiling ? No, they're for the non-original carrying strap. The strap is essential as the end fittings hold the keyboard in place when the machine is stored. Not having the originals, I made some replacements from aluminium strip and bar. The eyebolts are fittted into tapped holes in the bars. I then clipped the shoulder strap from a sports bag type thing onto the eyebolts to be able to carry the machine. To be honest the strap doesn't feel strong enough. I am pretty sure _my_ metal parts are at least as strong as the original plastic ones, but I will try to get a better strap before I carry the machine about too much. Calling the machine 'portable' is stretching things a bit too. It's heaver than a lot of the desktop machines I have (albeit the latter without monitor and keyboard). I feel the P2000C was portable in the sense that you could carry it from the office/lab to the lift, down in the lift to the car park and put it in the boot of your car to take it home or for an off-site job. Not portable in the sense that you'd take it across the country on public transport. -tony
[cctalk] Re: Philips P2000C restoration
On Wed, Jan 25, 2023 at 10:41 AM jos via cctalk wrote: > >> It booted straight up > > Where's the fun in that? > > > > > Not much, agreed. But plenty of other stuff here to keep me occupied well > until I am 130 years old ! Oh yes, same with me. More projects than I could ever complete. But my house has a finite volume. So I try not to buy things that are of little interest. -tony
[cctalk] Re: Philips P2000C restoration
On Wed, Jan 25, 2023 at 7:41 AM Tom Hunter via cctalk wrote: > > Thank you Tony for your well written and informative post describing the > restoration of a Philips P2000C luggable. > I wish there would be more posts like yours. Thanks. I've put a few photos of the machine (in bits) in my flickr account here : https://www.flickr.com/photos/tony_duell/albums/72177720304931970 Feel free to take a look. -tony
[cctalk] Re: Philips P2000C restoration
On Wed, Jan 25, 2023 at 7:52 AM jos via cctalk wrote: > > > Interesting and detailed description, thanks ! > > my P2000C "restauration" was much simpler : > > I picked it up, including carrying case and all the original disks, from the > e-waste ( illegally..) and found it be be in pristine condition, > > It booted straight up Where's the fun in that? -tony
[cctalk] Re: Philips P2000C add-ons.
On Tue, Jan 24, 2023 at 7:47 PM Will Cooke via cctalk wrote: > > > > > On 01/24/2023 11:09 AM CST Tony Duell via cctalk > > wrote: > > > > > > A couple of questions if anyone has experience of this machine : > > > > 1) There is a 5 pin DIN socket for connecting an external video > > monitor. The signals seem to be TTL-level separate syncs at European > > TV rates (15625Hz horizontal, 50Hz vertical) and separate (not > > composite) 4-level analogue video. > > > > I believe Philips sold a 12" monitor to connect there. What was the > > model number? Is a service manual availabe? > > > > Has anybody linked other monitors to that socket? > > > > In the US in the late 80s and 90s, there were a crap ton of similar monitors > (without case) sold on the surplus market. I had one. I believe they were > mostly Mitsubishi / Panasonic. Most of them were 9" with a lesser number of > 12". They had an edge connector for the power, ground, H sync, V sync, and > video inputs. Of course, in the US, they were 15750 / 60 Hz sync. I can > only guess what their original purpose was, but they were easy to connect to > a PC RGB video card (four resistors got you 16 gray shades.) So that > interface wasn't too uncommon. Perhaps there is/was something similar > available on the other side of the pond? Quite common, over here too. The interface is normally a 10 pin 0.156" edge connector carrying the signals you mention along with ground, +12V and (often) 3 wires to the brightness control. In fact the VT100 terminal has such a monitor PCB inside it. The internal monitor of the P2000C is similar, it has a header connector with +12V, ground, syncs, video on it. Oddly it's a Mitsubishi unit, for all Philips were making suitable CRTs, flyback transformers, etc at the time. > Maybe the reason you can't find any trace of the Philips add-on is for the > same reasons you suggest -- marketing realized it was of little value prior > to releasing it. > > > > 2) There is a 50 pin card edge for a SASI interface. I think the > > Philips hard disk unit used the Xebec S1410 controller. I've > > downloaded the user manual for that from bitsavers which at least > > gives me the command set. > > > > Does anyone have experience of a SASI-flash memory interface? Any > > recomendations for things to look at? Or should I design my own, it > > doesn't appear too hard? > > > > I have an Ampro Little Board Plus, which is a single-board Z80 computer the > size of a 5 1/4" disk drive. The "plus" means it has a SCSI interface. A > couple of years ago I was planning to build a flash disk for it and dug > through a lot of specs and bios code. Original SCSI was almost identical to > SASI and they were often interchangeable. The protocol is rather simple, as > you stated. What I found in the Ampro bios code was that for reading and > writing only about 4 commands were used. Another small number were used for > formatting. I think, iirc, there were two types of read and two types of > write. I never got around to building the thing, but it should be pretty > simple. I would also be rather surprised if no one else has done it. But if > you have the P-2000 bios code, you could take a look. I suspect it would be > very similar to the Ampro code. Alas there is no source of either the CBIOS or the boot ROM in any of the P2000C manuals and I suspect such source was never released. But it should be possible to kludge up something to do the SASI handshake and see just what does come out of that port when I try to boot from a hard disk or whatever. -tony
