Re: Ferroresonant transformer supply repair
måndag 9 september 2019 skrev Kyle Owen via cctalk : > On Sun, Sep 8, 2019, 20:39 Guy Dunphy via cctalk > wrote: > > > > > > >We recently replaced the ferroresonant capacitor in a power supply on > the > > CHM's > > >PDP-1. They do fail (thankfully, not often) - and they are not > > super-critical > > >as to value. If the one you're replacing has the same marked value, you > > should > > >be fine. > > > > > > > Yes, that's right. Find something with the same marked capacitance value. > > The rated voltage can be the same or higher. > > > > I can't seem to find motor caps that meet the voltage spec of 660V. 8uF > doesn't seem like a problem, but the combination together isn't looking > good. Are there any specific vendors I should be looking at? My usual > suspect of DigiKey isn't looking good. Mouser has CDE 8 uF 660 VAC. 11 are on order from the manufacturer. https://www.mouser.se/ProductDetail/Cornell-Dubilier-CDE/SFA66T8K475B-F?qs=sGAEpiMZZMu3dWSqd4Tl0A9wIZdhZWWRKQi0fpV8QTUDmNGSFUtTTQ%3D%3D I have replaced several of these capacitors in PDP-8, LA30, PDP-9. /Mattis > Thanks! > > Kyle > > > >
Re: Ferroresonant transformer supply repair
On 9/8/19 7:41 PM, Kyle Owen via cctalk wrote: > I can't seem to find motor caps that meet the voltage spec of 660V. 8uF > doesn't seem like a problem, but the combination together isn't looking > good. Are there any specific vendors I should be looking at? My usual > suspect of DigiKey isn't looking good. What capacitance do you require? For motor start/run capacitors, I tend to stay away from Chinese ones--they just don't seem to last. Try googling for "660VAC capacitor". They don't seem to be terribly difficult to find. Amazon even sells them. --Chuck
Re: Ferroresonant transformer supply repair
On Sun, Sep 8, 2019, 20:39 Guy Dunphy via cctalk wrote: > > > >We recently replaced the ferroresonant capacitor in a power supply on the > CHM's > >PDP-1. They do fail (thankfully, not often) - and they are not > super-critical > >as to value. If the one you're replacing has the same marked value, you > should > >be fine. > > > > Yes, that's right. Find something with the same marked capacitance value. > The rated voltage can be the same or higher. > I can't seem to find motor caps that meet the voltage spec of 660V. 8uF doesn't seem like a problem, but the combination together isn't looking good. Are there any specific vendors I should be looking at? My usual suspect of DigiKey isn't looking good. Thanks! Kyle >
Re: Ferroresonant transformer supply repair
At 04:54 PM 8/09/2019 -0700, you wrote: >Hi Kyle, > >On Sun, 8 Sep 2019 18:42:06 -0500 >Kyle Owen via cctalk wrote: > >> Has anyone replaced the capacitor in a ferroresonant power supply with much >> success? My current understanding is that the capacitor and transformer are >> mated as a pair, so replacing just one of them would require careful >> consideration. >> >> The PDP-8/I I'm working on has a 704A in it, with a GE 8uF 660V capacitor. >> It measures a couple of nF on my capacitor meter, and I was told by the >> previous owner that it's dead. > >We recently replaced the ferroresonant capacitor in a power supply on the CHM's >PDP-1. They do fail (thankfully, not often) - and they are not super-critical >as to value. If the one you're replacing has the same marked value, you should >be fine. > >Cheers, >Lyle >PDP-1 Restoration Team, CHM Yes, that's right. Find something with the same marked capacitance value. The rated voltage can be the same or higher. Be aware these are non-polarized caps, NOT electrolytics. They are typically paper, foil and oil. Best to find a new replacement, as many old-old oil- insulated caps will contain PCB (polychlorinated biphenyl) oil, which is severely carcinogenic. Banned, and must be disposed of as contaminated waste. Guy
ISO old AST mainframe comms driver software
AST-coax, AST-432, AST-SNA, etc. IBM comms products circa late 80s I'm in the process of pdf-ing the manuals this afternoon. The only product disk I have is AST-3780
Re: Ferroresonant transformer supply repair
Hi Kyle, On Sun, 8 Sep 2019 18:42:06 -0500 Kyle Owen via cctalk wrote: > Has anyone replaced the capacitor in a ferroresonant power supply with much > success? My current understanding is that the capacitor and transformer are > mated as a pair, so replacing just one of them would require careful > consideration. > > The PDP-8/I I'm working on has a 704A in it, with a GE 8uF 660V capacitor. > It measures a couple of nF on my capacitor meter, and I was told by the > previous owner that it's dead. We recently replaced the ferroresonant capacitor in a power supply on the CHM's PDP-1. They do fail (thankfully, not often) - and they are not super-critical as to value. If the one you're replacing has the same marked value, you should be fine. Cheers, Lyle PDP-1 Restoration Team, CHM -- 73 NM6Y Bickley Consulting West Inc. https://bickleywest.com "Black holes are where God is dividing by zero"
Ferroresonant transformer supply repair
Has anyone replaced the capacitor in a ferroresonant power supply with much success? My current understanding is that the capacitor and transformer are mated as a pair, so replacing just one of them would require careful consideration. The PDP-8/I I'm working on has a 704A in it, with a GE 8uF 660V capacitor. It measures a couple of nF on my capacitor meter, and I was told by the previous owner that it's dead. Any advice? Thanks, Kyle
Announcing VCF Pacific Northwest 2020
The Vintage Computer Federation is pleased to announce Vintage Computer Festival Pacific Northwest 2020! We will be at Living Computers:Museum+Labs in Seattle Washington on Saturday March 21st and Sunday March 22nd, 2020. To make this happen we are looking for exhibitors, speakers and volunteers. Last year we had 28 exhibits and 6 presentations. We had a great time, we broke the museum attendance record (again), and we are looking to have a good time again in March. If you are thinking of traveling from outside of the region there is plenty to do in Seattle while you are here. Local attractions include the Connections Museum, the Pacific Science Center, MoPOP, the Boeing factory tour, Mr. Rainier, etc. Victoria, British Columbia is also a short distance away. See a more complete list at https://goo.gl/3emMWH . Details about VCF PNW 2020 can be found at http://vcfed.org/vcf-pnw . The exhibitor registration instructions can be found at http://vcfed.org/vcf-pnw/exhibitor-registration . I'm happy to answer questions by email too. Regards, Mike mbbrut...@brutman.com or mich...@vcfed.org
Re: Looking for schematics of QBUS 32KW memory module.
On 9/8/19 4:21 PM, Mister PDP via cctalk wrote: I guess I should have been a little more specific about the memory issues I was having when I made this post. For the most part these issues seem to be scattered all about memory. Also, while the XXDP I have been running has been catching more or less the same addresses every time I run it, someones it misses a few or adds a few new ones. Moreover when the tests are done, I can read and write to the addresses using OTD just fine, which makes me think the chips that are bad (if they are bad, and it isn't some power related issue) are more flaky than dead. I put one of the outputs from a run of the XXDP test on a pastebin below. https://pastebin.com/mF6qWs0U If the voltage to these chips is not stable or at the correct voltages, the circuitry to refresh the dynamic memory might fail or read the wrong data level from the memory cells. Some chips may be more sensitive to slightly out of spec voltages than others. There of course may be a pattern in the outputs that suggest that have one or many bad memory chips, but I haven't zero'ed in on it yet. I have the same floppy controller sitting on project list for later in the year, so keep us posted as to your progress. Jerry
Re: Looking for schematics of QBUS 32KW memory module.
I guess I should have been a little more specific about the memory issues I was having when I made this post. For the most part these issues seem to be scattered all about memory. Also, while the XXDP I have been running has been catching more or less the same addresses every time I run it, someones it misses a few or adds a few new ones. Moreover when the tests are done, I can read and write to the addresses using OTD just fine, which makes me think the chips that are bad (if they are bad, and it isn't some power related issue) are more flaky than dead. I put one of the outputs from a run of the XXDP test on a pastebin below. https://pastebin.com/mF6qWs0U On Sun, Sep 8, 2019 at 4:01 PM Jerry Weiss via cctalk wrote: > On 9/8/19 3:20 PM, Noel Chiappa via cctalk wrote: > > > From: Mister PDP > > > > > listed back there were numerous bad addresses all over memory. > > > ... > > > I cannot find schematics for any of the boards > > > > . > > > > With the completed chart in hand, given a failing word (address and bad > > data), you can work out which chip is at fault, and replace it. Repeat > > for all memory errors. > > > > Noel's approach is valid and I have done the same on several boards. > Sorry I don't recognize the vendor of your board. > > I would also suggest checking the voltages on the board, especially the > -5V for the memory chip if the memory faults are scattered across the > memory space. The circuitry on the upper left of your picture is > probably a NE555 that is used as a charge pump to generate Vbb from the > LSI power supplies. > > The larger capacitors are probably tantalum (Kemet?) and should have > aged better than electrolytics of the period. > >Jerry >
Re: Looking for schematics of QBUS 32KW memory module.
On 9/8/19 3:20 PM, Noel Chiappa via cctalk wrote: > From: Mister PDP > listed back there were numerous bad addresses all over memory. > ... > I cannot find schematics for any of the boards . With the completed chart in hand, given a failing word (address and bad data), you can work out which chip is at fault, and replace it. Repeat for all memory errors. Noel's approach is valid and I have done the same on several boards. Sorry I don't recognize the vendor of your board. I would also suggest checking the voltages on the board, especially the -5V for the memory chip if the memory faults are scattered across the memory space. The circuitry on the upper left of your picture is probably a NE555 that is used as a charge pump to generate Vbb from the LSI power supplies. The larger capacitors are probably tantalum (Kemet?) and should have aged better than electrolytics of the period. Jerry
Re: Looking for schematics of QBUS 32KW memory module.
> From: Mister PDP > listed back there were numerous bad addresses all over memory. > ... > I cannot find schematics for any of the boards You can repair MOS memory boards where the board is basically working, but just has some failing memory chips, without schematics. First you need to create a map which translates memory chip # to bits. You have 32 chips in the array, so there are probably 2 32KB banks, each 16 bits wide. Pull a chip, and then try and figure out which bit it is; then repeat with other chips to try and figure out which bits are stored in which chips. (Unless the designers were insane, each chip will hold the same bit in all the words in that bank.) On yours, the memory chips are in sockets, which makes this less painful. (On boards where the chips are soldered in, a program which loops, storing a word with a single 1 bit, can be used to the same effect; the chip data sheet will tell you which pin is the data pin.) Usually a missing chip results in bits stored in that chip reading as '0', but it's possible they will read back as 1. Anyway, to test the first possibility, start by finding a location in the each bank that can be written to all 0's and all 1's (read back after writing to verify). Next, pull a chip, and then try writing all 1's to that word in the low bank, and read it back. If it now has a 0 bit, congratulations i) you've verified that missing chips read as 0, ii) that chip is part of the low bank, and iii) the 0 bit tells you which bit that chip is - fill in that entry in your chip<->bit chart. If not, try the high bank word, and see if it now has a 0 bit. If not, try writing 0's to the high and low words, and check for a '1' bit; if so, i) missing chips read as 1, etc. If neither is true, check back here! Otherwise, try pulling another chip, and work out which bit that one is, and add it to the chart. Repeat for all 32 chips - although if you're lucky, after a couple you might find a pattern, and be able to predict which chips hold which bits. (But not always; many are random; see e.g.: http://gunkies.org/wiki/Q-RAM_11 http://gunkies.org/wiki/NS23M for some.) If so, do a few spot tests of your predictions to make sure your pattern is correct. With the completed chart in hand, given a failing word (address and bad data), you can work out which chip is at fault, and replace it. Repeat for all memory errors. Noel
Looking for schematics of QBUS 32KW memory module.
Hello, A few weeks ago I ordered a Sigma 400255 for my H11A LSI-11 computer with the hopes of getting a 8" floppy hooked up for VCFMW. For the most part, all the tests I ran from the ODT seemed to be AOK. The one this I couldn't do it boot RT-11 from my TU58 emulator, as it would crash every time. Every since I was able to boot RT-11 on my machine it has been unstable and prone to crashes, but i chalked that up to the TU58 emulator, and not the machine itself. Since I needed to boot from to TU58 in order to INIT and make a bootable RT-11 disk for my system, I looked for other causes for the crashes. I ran the VKAA XXDP test, which passed fine. I then ZKMA test, which lo and behold listed back there were numerous bad addresses all over memory. The only memory modules I have are 3 nearly identical 3rd party 32KW memory modules. The one that I have in the system right now came with it, and is the one with memory errors. The other two are ones I bought on eBay that are in rather poor condition and currently do not work at all. I was hoping to transfer some of the 4116 chips from my nonfunctional units over to my semi-functional unit, but I cannot find schematics for any of the boards because they don't have any marking identifying marking on them. If anyone knows where I can find schematics for these boards, that would be wonderful. I am including a picture of one of these boards below. https://i.ibb.co/sQwZw0j/32kwram.jpg Thank You, Gavin Tersteeg
Re: Info on testing vintage power supplies
On 9/2/19 9:56 AM, Tony Duell wrote: On Mon, Sep 2, 2019 at 5:35 PM Alan Perry via cctech wrote: Can anyone here provide a pointer to info on testing vintage power supplies? Search results on the web may eventually lead to the kind of info that I am looking for, but I have to get through too many pages of modern PC power supplies first. Specifically, I will be testing the power supplies in my Sun 3/260, which has 24V, 12V and 5V. I am wondering things like what is suitable loads and do I need to put a load on all three or can I test them one at a time and what I haven't thought of with regards to testing them. With most classic computer switch mode PSUs (which the one in a Sun 3/260 is), you need to load the main output. The other outputs don't _need_ loads, but it doesn't hurt to have them). For 99% of classic computer supples (and true for the Sun 3/260) the main output is the +5V one. I'd try to draw perhaps 5A from that. So a 6V car bulb of 30-odd watts. A 6V car headlamp bulb, for example. It's not critical Have that connected between the +5V output and ground (the 0V rail of the machine, not necessarily mains ground) for all tests on the supply. In other words, connect up the bulb, power up (the bulb should light), then measure the voltage between each output of the supply and ground. The power supplies that I had been looking at were the two in the SMD disk cabinet. Still haven't tried powering them up. Today I opened the 3/260 cabinet. There was a nest made by some rodent on top of its power supply. It was composed of shredded material that went down into the power supply through the holes in its cover. From the surface rust, it looks like there was moisture in the nest. What should I do to the power supply before trying to power it up? alan
Shugart-Interface 8" Floppy Diskette Drive Configurability
I've been contemplating a floppy diskette drive emulator with features to make it fit better into systems using 50-pin Shugart style floppy drive interfaces vs. the other emulators already on the market. Studying manuals for various 8" floppy diskette drives, I see that they generally provided a great deal of configurability. There are the myriad of jumper-selectable options which change drive behavior for compatibility with various computers. Then there are features like FM data separators which are present on some, but not all, drives. And then there are many documented "cut this trace, then bodge wire this signal to pin X of the edge connector" options for special purposes such as individual drive motor controls, simultaneous monitoring of all four drive ready signals, etc. Since fully supporting all of the options I've seen documented would have real hardware cost and add complexity to the design, I'm wondering just how much of that configurability is really necessary. Which non-default options are really needed for system still in use and/or in the hands of collectors? Which were only ever provided for some obscure industrial system manufacturer, with no surviving systems in existence? Which were included just in case somebody might need them, but were never used in practice? I'd appreciate it if anybody can provide insight into this, such as examples of systems which required non-omnipresent and/or non-default configuration options. -- Mark J. Blair, NF6X http://www.nf6x.net/
