Re: H786 power supply help wanted
On 03/30/2019 07:50 PM, Charles via cctalk wrote: Update: I removed the H786 from the chassis, and set it up on the workbench with loads on the +5 and +12. No output. 320V across the half-bridge, but no +12 Startup. Found I had forgotten to put a cliplead to the primary of the startup transformer. Turned it on and it works... 5 and 12 volts into 1 ohm and 4.7 ohm respectively. WTF. So I disconnected the PC supply, put the H786 back in, and it fired right up (including the real-time clock) and I ran it for half an hour. Go figure. Ain’t classic computers fun sometimes... Connectors, always flaky connectors! Jon
Re: H786 power supply help wanted
Update: I removed the H786 from the chassis, and set it up on the workbench with loads on the +5 and +12. No output. 320V across the half-bridge, but no +12 Startup. Found I had forgotten to put a cliplead to the primary of the startup transformer. Turned it on and it works... 5 and 12 volts into 1 ohm and 4.7 ohm respectively. WTF. So I disconnected the PC supply, put the H786 back in, and it fired right up (including the real-time clock) and I ran it for half an hour. Go figure. Ain’t classic computers fun sometimes... From: Paul Anderson Sent: Saturday, March 30, 2019 3:26 PM To: Charles ; General Discussion: On-Topic and Off-Topic Posts Subject: Re: H786 power supply help wanted Hi Charles, The H786 was standard for the 11/23, BA11-N. The H7861 was for the 11/23+, BA11-S and had afrw more amps of +5 volts. I would start by looking at the electronic caps. I have a few extras here but am pretty busy for the next week or so. Paul On Sat, Mar 30, 2019 at 2:25 PM Charles via cctalk wrote: I have a PDP-11/23+ and the power supply (H786) "last ran when parked" a year or so ago. But there's no DC output at all today, and the fans are running so there is AC power... I also have the original H7861 that came with it, which had a blown chopper transistor. I couldn't find anything else bad, so I replaced the transistor and within a few seconds of running, it blew again. :( So I need some help - I've never been good at fixing switching supplies, not to mention the high-side hazards. The simplest solution would be just to replace it with a working unit. Anyone got one to sell, hopefully cheap? :) If not, can anyone fix one or both of mine? thanks! Charles
Re: H786 power supply help wanted
On 3/30/2019 2:25 PM, Charles via cctalk wrote: > I have a PDP-11/23+ and the power supply (H786) "last ran when parked" a > year or so ago. But there's no DC output at all today, and the fans are > running so there is AC power... > I also have the original H7861 that came with it, which had a blown > chopper transistor. I couldn't find anything else bad, so I replaced the > transistor and within a few seconds of running, it blew again. :( > > So I need some help - I've never been good at fixing switching supplies, > not to mention the high-side hazards. > The simplest solution would be just to replace it with a working unit. > Anyone got one to sell, hopefully cheap? :) > If not, can anyone fix one or both of mine? > > thanks! > Charles > Sorry, no spares (and certainly no tested spares. ;) ). My playbook for these sorts of things goes like this. Others will undoubtedly chime in with probably better advice. 1. Is anything obviously burned / overheated / fuses blow? Note those, and what feeds them. 2. Check the semiconductors - often I will lift one leg of a diode or two legs of a transistor to make sure I get a good test. It's a pain, but usually worth it. Sometimes, depending on what the schematic looks like, I'll test without lifting as many / any legs. 3. Specialized regulators / op-amps, etc., require checking their voltage while running. Not usually easy to test them. 4. Check the capacitors, especially input and output for excessive leakage. I often will reform input and output caps just because. Check their ESR, at least with one of the cheap component testers out there. I use one of these for testing, as well as an ohmmeter, etc. https://www.ebay.com/itm/All-in-1-LCR-Component-Tester-Transistor-Diode-CapacitanceESR-Meter-InductanceBH/183706764001 I also use a "Blue ESR Meter" of late, as well: https://anatekinstruments.com/products/anatek-blue-esr-meter-full-kit-for-self-assembly-besr_kit But before I had these, I just used an ohmmeter to test each semiconductor junction, and monitored voltage while reforming capacitors to get an idea of their ESR.
Using PC power supply in BA-11S
Regarding my earlier request for help repairing an H786 and H7861, it occurred to me that I could instead use a desktop PC power supply, having several in the junkbox. It's even small enough to fit in there once the H786 is removed. So I patched the wiring harness from the PC supply to the screw terminals on the backplane... 5 and 12 volts at the terminals, Fault lights on the RL's went out, but no green light on the KDF-11B. After a look at the schematics, the simple solution was just to pull the power monitor daughter-card from the H786, so the power OK lines (8640 buffer inputs, DC OK and Power OK) are not being pulled down. Green light on, memory test ran, and boots RT-11 from RL02 :) A better fix will be to drive the DCOK and POK lines from the PC supply, which appears to have a "P.G." orange wire (I'm betting "Power Good" but will check it out first). TSX-Plus won't run though, because there's no real-time clock. Looks like a small transformer and a bit of buffer circuitry is needed to generate a 60 Hz TTL pulse. Or a dongle with a 555 or crystal oscillator. I may have a try at fixing the original supply before going to the trouble (including mounting the PC supply in the chassis and jumpering the two ribbon cables together). Speaking of trouble, today I learned that the "Restraining Cable Stud" mentioned in the 11/23 user manual is not just there for decoration. For the first time (ever), the BA-11S chassis overbalanced and fell out of the front of the cabinet. It hit the floor with a crash while yanking all the ribbon cables off (without breaking anything, incredibly, including a near miss to my feet in socks!) Perhaps installing that cable is a good idea ;) -Charles
Re: H786 power supply help wanted
Hi Charles, The H786 was standard for the 11/23, BA11-N. The H7861 was for the 11/23+, BA11-S and had afrw more amps of +5 volts. I would start by looking at the electronic caps. I have a few extras here but am pretty busy for the next week or so. Paul On Sat, Mar 30, 2019 at 2:25 PM Charles via cctalk wrote: > I have a PDP-11/23+ and the power supply (H786) "last ran when parked" a > year or so ago. But there's no DC output at all today, and the fans are > running so there is AC power... > I also have the original H7861 that came with it, which had a blown > chopper > transistor. I couldn't find anything else bad, so I replaced the > transistor > and within a few seconds of running, it blew again. :( > > So I need some help - I've never been good at fixing switching supplies, > not > to mention the high-side hazards. > The simplest solution would be just to replace it with a working unit. > Anyone got one to sell, hopefully cheap? :) > If not, can anyone fix one or both of mine? > > thanks! > Charles > > >
Re: AGC restoration / was Re: PDP-8 signed overflow detection - Apollo guidace computer
Yes, that would be Carl’s “day to day” blog (http://rescue1130.blogspot.com/). He is also on the list, lurking in the background. Carl, are you there? Ken Shirriff has also several deeply researched blog articles on specific AGC topics (righto.com). Mike has some very interesting posts on his AGC FPGA emulation work here: http://mikestewart.hcoop.net/ Marc > On Mar 26, 2019, at 10:43 AM, Brent Hilpert via cctalk > wrote: > > On 2019-Mar-26, at 9:28 AM, Noel Chiappa via cctalk wrote: >>> From: Ben Bfranchuk >> >>> Now they seem to have have found a SCRAPPED Apollo guidance >>> computer and am rebuilding the missing pieces. >> >> Wow. What a great site (and that guy has mad skills, everything from >> repairing old Teletypes, through designing boards, to repairing analog >> stuff). Just 'wasted' a good chunk of the morning reading back through >> it; tons of really neat things (including recovery of the very first >> FORTH, along with a lot of Diablo drive - from the Alto - repairs). >> >> As a shortcut, here: >> >> http://rescue1130.blogspot.com/2018/11/ >> >> is the backstory on the AGC; about 1/3 of the way down, in "Restoring an >> Apollo Guidance Computer, part V". > > > > This is the same AGC restoration that curious marc has been making videos > about: > >https://www.youtube.com/watch?v=2KSahAoOLdU > > The project and videos were mentioned on the list back in December. > There's an interview with Jimmie there (4:13) with more details about the > backstory. >
H786 power supply help wanted
I have a PDP-11/23+ and the power supply (H786) "last ran when parked" a year or so ago. But there's no DC output at all today, and the fans are running so there is AC power... I also have the original H7861 that came with it, which had a blown chopper transistor. I couldn't find anything else bad, so I replaced the transistor and within a few seconds of running, it blew again. :( So I need some help - I've never been good at fixing switching supplies, not to mention the high-side hazards. The simplest solution would be just to replace it with a working unit. Anyone got one to sell, hopefully cheap? :) If not, can anyone fix one or both of mine? thanks! Charles
Re: IBM 360 Model 50 information?
> My experience with IBM legal (who were actually quite communicative when > I approached them) on that front with IBM 1410 manuals suggests to me > that they will not ever give explicit permission, because nobody at IBM > will ever by confident that they won't end up giving away some trade > secret or other. We (Techworks in Binghamton, NY) work with the archivist quite a bit, and are a=on very good terms. Nope, they simply did not keep much from that era. It was probably disposed of back when IBM was in trouble 30 years ago. -- Will
Re: IBM 360 Model 50 information?
On 3/30/2019 12:35 PM, Noel Chiappa via cctalk wrote: > > From: Al Kossow > > > Decades later, people are still afraid to release them. I tried to get > > 2065 ALDs from someone that had them and they wouldn't give them to me. > > Sounds like it's time to have someone high up at the CHM talk to someone > at IBM to get an OK; if you only ask for permission, not for IBM to cough > up the info themselves, that might be doable. > > I'd try and get a blanket OK for anything more than 20 years old, i) that > should be long enough that they'd be OK with it, ii) a moving thing like > that would mean you wouldn't have to go back again. > > Noel > My experience with IBM legal (who were actually quite communicative when I approached them) on that front with IBM 1410 manuals suggests to me that they will not ever give explicit permission, because nobody at IBM will ever by confident that they won't end up giving away some trade secret or other. Even when they know the risk is nonexistant, it isn't possible to get anyone to sign off on it. So instead we (meaning the collective community) are left with a situation where IBM's failure to send a cease and desist letter of some sort becomes a kind of tacit permission. I suspect, but do not know of course, that the reasons that the owners would not part with their copies was concern over losing them or concern over their value becoming diminished by having scanned copies around. JRJ
Re: IBM 360 Model 50 information?
> Sounds like it's time to have someone high up at the CHM talk to someone > at IBM to get an OK; if you only ask for permission, not for IBM to cough > up the info themselves, that might be doable. It is very likely IBM does not have the information anymore - at least not in the archives. Maybe in some forgotten closet or abandoned office. -- Will
Re: IBM 360 Model 50 information?
> From: Al Kossow > Decades later, people are still afraid to release them. I tried to get > 2065 ALDs from someone that had them and they wouldn't give them to me. Sounds like it's time to have someone high up at the CHM talk to someone at IBM to get an OK; if you only ask for permission, not for IBM to cough up the info themselves, that might be doable. I'd try and get a blanket OK for anything more than 20 years old, i) that should be long enough that they'd be OK with it, ii) a moving thing like that would mean you wouldn't have to go back again. Noel
Re: IBM 360 Model 50 information?
On 3/29/19 9:12 PM, Curious Marc via cctalk wrote: > Which brings us to the real problem: we don’t have 360 Model 50 ALDs. Anyone > has them? I've been looking for years. The few on bitsavers is all I've ever been able to get. Decades later, people are still afraid to release them. I tried to get 2065 ALDs from someone that had them and they wouldn't give them to me.
