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DOA PETs. (2001-8, 4032 and 8032)

Dabone you can get good results on the Vic 20 using a heat gun. I've removed the 2114 out of my Vic 20 using the heat gun without damaging the board or the chips. If its a scrap board it's worth practicing on with nothing to lose. Use an embossing type heat gun though and not the paint stripping type they are less harsh but be warned can still do damage!
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For me, I usually use my hot air rework station and some liquid flux. I just use this motherboard as art.

Later,
dabone
 
Dabone you posh so and so!!:D Hot air rework stations, spares as wallpaper!!

I have to sweat it out with hoping I dont do damage! Only Joking!! ;)

Are they easy to use?
 
gubbish said:
I got replacement 2114s for my PETs from Jameco...
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Thanks for all the 2114 source suggestions, but I'm 99.9997% positive that using them instead of 2149s won't make any difference. (The only difference between the parts is that 2149s are *much* faster, and they don't support a low-power mode that 2114s do but isn't used by the PET anyway.) The friend I gave the 2001-8 to replaced his video memory (which *was* bad) with 2149s from the same source I got mine from and they're working fine.

I need to look more closely, but I'm starting to be convinced there's a pattern to the screen corruption which lends further credence to the idea it's a flaw in the addressing circuitry. (Once I've done the counting to prove/disprove my pattern hypothesis I'll explain it.) The problem is offhandedly I'm not sure how the pattern translates to a troubleshooting strategy.
 
dave_m said:
Check out this user manual for disk syntax...
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My confusion over this is that it doesn't appear to me that the PET is communicating with the drive at all, yet disk commands that involve writing to it just silently return to READY instead of saying "DEVICE NOT READY" or something. I don't have the experience to know if *that* is normal. (is it?) I can run the same commands with the drives completely disconnected and the results are the same. (Silent return, no error.)

I'm going to spend some quality time doing continuity testing from the various ICs to the IEEE connector on the PET, and then see if I get continuity through the cable when it's plugged in. The edge connector on the board is in absolutely horrible shape. (Badly corroded.) I've gotten it as clean as I can with alcohol and erasers, but... is there any good way to actually try to restore it? I remember long ago seeing adds for products to silver or gold-plate the tin edge connectors on the back of TRS-80 Model I keyboard units to improve the reliability of the expansion interface connector, is there a similar product I could paint or melt onto the PET's connectors?
 
Progress! Awesome!

Eudimorphodon said:
Next thing I did was try rotating another 2149 (supposedly a suitable replacement for 2114s, which I haven't been able to find locally)
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2114s can be had from Jameco. They're local if you want to do will-call, or they can ship from their Belmont store. That's where I got mine.

Eudimorphodon said:
The last thing I've attempted was to try wiring up a couple of the disk drives I picked up. Using the best-looking IEEE-488 cable I had on hand I tried an MSD SD-1 and and an 8050, as both were passing diagnostics. Here's where I have to ask some dumb questions, since I'm barely at all familiar with Commodore disk usage. When I type "CATALOG" or attempt to save a file to disk (with either DSAVE or SAVE "name",8) the PET is immediately returning to the READY prompt, without the disk drive spinning at all. Meanwhile, If I attempt to load a file again the drives don't respond at all and the PET simply spits out a ?FILE NOT FOUND error.
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I had the exact same issue with my 8032 and my SD card reader prototype. Turns out it was just a dirty connector. No, seriously! I used a soft eraser on the IEEE-488 card edge connector on the PET motherboard, and then some contact cleaner. Put the cable back on, and blammo! Suddenly, it worked just fine!

Of course, I can also give you one of my not-quite-correct-but-still-working prototype boards to experiment with, so you have a known-good value.

EDIT: As a P.S., I should point out that the connector didn't even LOOK very dirty. Yeah, it was dull and not shiny, but I wouldn't have guessed that it would have caused an electrical fault. Still, apparently it did need cleaning.
 
Twylo said:
I had the exact same issue with my 8032 and my SD card reader prototype. Turns out it was just a dirty connector. No, seriously! I used a soft eraser on the IEEE-488 card edge connector on the PET motherboard, and then some contact cleaner. Put the cable back on, and blammo! Suddenly, it worked just fine!

Of course, I can also give you one of my not-quite-correct-but-still-working prototype boards to experiment with, so you have a known-good value.

EDIT: As a P.S., I should point out that the connector didn't even LOOK very dirty. Yeah, it was dull and not shiny, but I wouldn't have guessed that it would have caused an electrical fault. Still, apparently it did need cleaning.
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I guess I can try some contact cleaner. I'm just sort of worried that I'm actually going to take the copper off at a certain point. There's green oxidation I don't seem to be able to even budge with anything else.

It still seems weird to me that disk-related commands don't seem to use even basic handshaking to let the user know if the disk drive appeared to be listening or not, but I suppose it was the 1970's...

That would be completely awesome if you could loan me one of your known-working IEEE boards to try to get some idea if my PET is deaf, dumb, or just filthy. You're certainly welcome in return to borrow any of the IEEE peripherals I have if you want to investigate chaining your SD card reader with "real" PET drives, etc. I'll send you a PM.
 
Eudimorphodon said:
...It still seems weird to me that disk-related commands don't seem to use even basic handshaking to let the user know if the disk drive appeared to be listening or not, but I suppose it was the 1970's...
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???

Assuming BASIC4, if the drive is unplugged or does not respond at all you should see "device not present error"; if it has an error, then the red indicator should light and "? DS$" should tell you what the error was, so it sounds like you have (another) problem somewhere. It should be pretty simple to at least test continuity from the PET IEEE drivers to the drive; the connecting fingers in the IEEE connectors sometimes push out the back so you might want to inspect those while you're at it. Also check to make sure that the drive's ID hasn't been changed from the standard #8.

BTW, I added a small piezo beeper across the status LED on my drives because unless you look at it it's not always obvious that there was an error.
 
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MikeS said:
???

Assuming BASIC4, if the drive is unplugged or does not respond at all you should see "device not present error"; if it has an error, then the red indicator should light and "? DS$" should tell you what the error was, so it sounds like you have (another) problem somewhere.
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Okay, so... yeah, that's where I'm really confused. If I unplug the IEEE cable from the PET *entirely* and try to "SAVE "program",8" or something else that should use the a disk drive it simply returns to the READY prompt with no error. If that is *not* normal behavior (and as I noted, I'd be surprised if it was) I'm wondering what's short-circuiting the handshake.
 
Hmm... yeah, I just tried VICE and it does indeed just return to READY with no error and no, that's not normal.

But I'm not very familiar with VICE; even after detaching all disk images cAd0,U9 still lists a directory, so maybe I just haven't really 'unplugged' the drive or even 'removed the disk'.

Which drive are you using? If the 8050, what's the status of the LEDs?

Dave, Anders, what say?
 
MikeS said:
Hmm... yeah, I just tried VICE and it does indeed just return to READY with no error and no, that's not normal.

But I'm not very familiar with VICE; even after detaching all disk images cAd0,U9 still lists a directory, so maybe I just haven't really 'unplugged' the drive or even 'removed the disk'.
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I've tried going to the "peripherals" menu in VICE and setting device type for 8 through 11 as "none". And when I do that it reproduces what I'm seeing, but I'm getting the feeling that in several areas VICE doesn't really duplicate the bare-metal hardware. Perhaps it "short-circuits" IEEE transactions to virtual drives in some way that happens to replicate whatever is "short-circuiting" any status tests on the real thing?

I guess I need to read up on how a conversation across IEEE-488 actually works.

Which drive are you using? If the 8050, what's the status of the LEDs?
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On the 8050 when it's powered up it flashes all its LEDs red for a few seconds and then settles down with the drive LEDs dark and the "main" indicator LED green. (which seems to indicate a successful self-test.) Nothing I do on the PET when it's cabled up affects it at all. (no blinking, no disk spinning, nothing.) Same deal with the MSD-1. Powered on its main indicator turns green after a couple seconds, but it's completely deaf to anything the PET might be saying. (Assuming it's saying anything at all.)
 
As Mike said, if the drive is disconnected you should get a "device not present" message.
It's possible that the NRFD (not ready for data) line is stuck high. The pet looks for this signal immediately after asserting the ATN line when it's about to do a transaction. The device would bring NRFD high after seeing the ATN. If you disconnect everything, and check out the NRFD signal, that might show something.
NRFD would be pin 7 on the PET IEEE connector. I believe it should normally be low if no devices are connected, so if it's stuck high that would explain why everything just says "ready"..
 
Since it's been a while I figured I might as well toss an update in here.

This weekend I "fixed" the 4032 by swapping in another motherboard. I received in trade a PET Dynamic motherboard with 32k but missing all the socketed chips. (It was even missing VRAM, but there were sockets installed for it.) I populated the board with a new set of 6520As, a 6522, a 6502B, a pair of 2149 SRAMs for video, and an EPROM copy of BASIC 4.0.

(I ended up having to pull the character generator ROM from my still-sick board, along with the C000 BASIC ROM... the latter because I was a complete bonehead and somehow managed to insert my EPROM C000 backwards. The notches on the EPROMs are not as obvious as the ones on the real chips but I still don't have much of an excuse. I was so careful for everything else. The board seems to have survived unscathed but the ROM is toast. What was sort of interesting was there weren't any fireworks with the ROM in backwards. The system just refused to run, even with the PETTESTER, until I saw the problem and yanked it out. I put it back in correctly but with it the system drops to debugger and a dump of the C000 memory space shows nothing but a repeating bit pattern. Live and learn, I guess.)

Anyway, with the new motherboard and another shot at cleaning the keyboard applying what I learned cleaning my new 4016's board the system seems to work great. I had to clean the IEEE-488 connector carefully to get it to recognize my PETDISK card reader but once done it was loading some downloaded games like a champ. (And thus I've learned there are a non-zero number of games out there that don't seem to behave correctly on a CRTC PET that work fine on a Dynamic. Or, well, I hope my 4016 doesn't have some bad RAM or something.)

Now that I have the working PET I'm trying to decide where to proceed with fixing the other motherboard. Getting the IEEE port working is probably a start. Before that, though, I do have a question that's undoubtedly covered somewhere but perhaps someone knows off the top of their head: What's a suitable EPROM replacement for the character generator? Looking at the pinouts and the size of the ROM image it looks like perhaps a 2716 would do it? I'd sort of like to get both boards fully populated so I don't have to swap parts between them during a troubleshooting session.
 
Eudimorphodon said:
And thus I've learned there are a non-zero number of games out there that don't seem to behave correctly on a CRTC PET that work fine on a Dynamic.
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I hope you did not run into a game with the "Killer Poke". Check to see if game does something like POKE 59458,32. This screws up a register contents in the 6545 CRTC.

What's a suitable EPROM replacement for the character generator? Looking at the pinouts and the size of the ROM image it looks like perhaps a 2716 would do it?
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Yes a 2716 will do the job. I think a 2732 will also work if you put the data in the upper 2K of the EPROM.
-Dave
 
dave_m said:
I hope you did not run into a game with the "Killer Poke". Check to see if game does something like POKE 59458,32. This screws up a register contents in the 6545 CRTC.
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I haven't seen any screen corruption from firing up a game yet, but... one "fer instance" is a game called "Millipede", a Centipede clone. It works perfectly on the 4032 while on the CRTC 4016 the keyboard controls don't seem to function correctly.

One thing that is getting pretty clear to me is if I intend to make regular use of these PETs it would be a good idea to add a RESET button. I found a page saying that pulling pin #2 on the 555 timer to ground should work to trigger a reset. Assuming that works I'll be picking up some momentary-contact pushbuttons next time I'm shopping for bits and pieces.

And thanks, I'll look into getting a 2716 burned along with a replacement BASIC ROM.

I spent some time looking at the monitor that came with the 2001-N I got the replacement motherboard in. At some point someone managed to break the corner off the circuit board inside of it. (Looking from the back it's the right corner, under the flyback transformer.) It *looks* to me like the entire edge of the circuit board is a ground plane, so I'm wondering if it might be possible to salvage the board, as it doesn't look to me like the break actually severed anything, but granted I haven't even powered up the monitor yet so I have no idea how far gone it is. (The person I got it from said it was dead.) I am impressed how "Chinese Puzzle"-ish it is; the back panel unscrews, but the rest of the monitor appears to be essentially a tube of plastic with the CRT screwed to the front and the monitor board hovering on standoffs under it. Getting access to the board to troubleshoot it (without inadvertently breaking it or killing oneself) looks like an interesting challenge. Maybe too interesting.
 
Eudimorphodon said:
One thing that is getting pretty clear to me is if I intend to make regular use of these PETs it would be a good idea to add a RESET button. I found a page saying that pulling pin #2 on the 555 timer to ground should work to trigger a reset.
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On all boards except the original board, you can find /RESET on the memory expansion connector J4 pin 22. There are two rows of header pins on this connector. If I remember correctly, all of the second row pins are grounds which is convenient for the second push-button wire.

If you still have control of the PET, a way to get a cold start in BASIC 4 is: SYS 64790 (Call to power up routine).
 
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