Commodore PET 2001 voltage regulators

[retromit]

Originally Posted by ScottishColin

Hi Tim - I have a spare (new) 6502 - see photo - which I have popped into my 3016 PET and checked that it works which you're welcome to if you want.

I also have a spare 40 pin turned-pin socket if you need it. Let me know.

Colin.

Hi Colin. That's very good of you and will send you a message.

Thanks,
Tim.

[ScottishColin]

Oh my goodness. Look at those cassettes.

So many memories there.

Colin.

Originally Posted by retromit

When I bought the PET it did come with a datasette and a selection of tapes. I've added a few pictures to show these (as well as a couple of books). There were also a number of other tapes, but these don't have labels, etc., so not sure what could be on them.

I haven't had a chance to go through any of these due to the issues faced. So I'm hoping to get something tested to see if any of the tapes load. I'm also thinking to put the BASIC toolkit back into UD5 as well to make sure it works in the PET - with the leg being repaired I'm hoping it would be okay, but would it be better (safer) to potentially burn a new EPROM for this?

Now that it seems to be functioning, it will be good to get some further tests carried out.

With you mentioning the SD solutions, I have seen one advertised from The Future was 8 bit. Has anyone any experience of the SD2PET?

Tim.

[Timbucus]

I have the C64 version of the SD2IEC and it is a great product as is everything I have from that supplier, so no reason not to suspect the PET one would not be excellent as well.

Originally Posted by retromit

... [Lovelly mention of original cassettes deleted]

With you mentioning the SD solutions, I have seen one advertised from The Future was 8 bit. Has anyone any experience of the SD2PET?

Tim.

[ajgriff]

Originally Posted by retromit

With you mentioning the SD solutions, I have seen one advertised from The Future was 8 bit. Has anyone any experience of the SD2PET?

No experience of the SD2PET as such but it's a product from Dave Curran of Tynemouth Software. Tynemouth has its own web based shop but Dave suspended operations early on in the pandemic and hasn't so far resumed direct sales. TFW8b.com has been the sales vehicle in the meantime although I don't know whether or not the site owner has been involved in making any of the products. Tynemouth itself seems to have an extremely good reputation amongst Commodore enthusiasts. From memory I believe Colin bought the spare 6502 mentioned earlier from there.

Alan

[ajgriff]

Originally Posted by retromit

When I bought the PET it did come with a datasette .....

Now that it [the PET] seems to be functioning, it will be good to get some further tests carried out.

Had to do quite a bit of work on the datasette (same black cased version) I acquired for my PET so if you have problems with your's let us know in due course.

Alan

[retromit]

Originally Posted by ajgriff

Had to do quite a bit of work on the datasette (same black cased version) I acquired for my PET so if you have problems with your's let us know in due course.

Alan

Thanks Alan. I'm hoping to get my tested tomorrow and see if it will load anything. Jumping the gun a little, but what did you find as the main issues?

Anything I should check before plugging into the PET/loading for the first time?

Tim.

[SiriusHardware]

before plugging into the PET/loading for the first time?

I'm sure you probably know this already but never, ever connect two items together or disconnect them from each other while the power is on. This applies even to the datasette, which is powered from the machine itself.

On tape drives this age the belt may have snapped or hardened, and on the tapes themselves, have a look to make sure that the brown or grey foam pressure pad in the hollow under the tape has not turned to sticky goo. If it has, obviously do not attempt to play the tape until that pad has been replaced.

[SiriusHardware]

You asked a question about the Daver2 test EPROM which I can't answer off the top of my head - don't have a PET to run it in, but if you remember the online archive I pointed you to via PM, that contained both the code and a well written user manual, so maybe have a look through that to see what the expected behaviour is. Colin may be able to confirm whether it behaves the same way for him because he does have both a machine and the test code.

We (or rather Slothie) know(s) exactly what the 'Slothie' test code should do and when it should do it because he wrote it.

Daver2 hangs out on the vintage computer forum (a search on VCFED will find it) and I'm sure he would be pleased to hear it is proving useful and to answer any queries you may have about it himself.

[ScottishColin]

I would replace the belts as a matter of course. They're very old now. Just search for 1530 C2N belt on eBay and you should find them cheap enough


Colin

Originally Posted by retromit

Thanks Alan. I'm hoping to get my tested tomorrow and see if it will load anything. Jumping the gun a little, but what did you find as the main issues?

Anything I should check before plugging into the PET/loading for the first time?

Tim.

[retromit]

Originally Posted by SiriusHardware

You asked a question about the Daver2 test EPROM which I can't answer off the top of my head - don't have a PET to run it in, but if you remember the online archive I pointed you to via PM, that contained both the code and a well written user manual, so maybe have a look through that to see what the expected behaviour is. Colin may be able to confirm whether it behaves the same way for him because he does have both a machine and the test code.

We (or rather Slothie) know(s) exactly what the 'Slothie' test code should do and when it should do it because he wrote it.

Daver2 hangs out on the vintage computer forum (a search on VCFED will find it) and I'm sure he would be pleased to hear it is proving useful and to answer any queries you may have about it himself.

Thanks, and apologies. I should have remembered to check the messages. I've just downloaded the manual and it looks to be working as expected. I'll run it through again tomorrow and make sure all looks okay. The manual does say that it could take a time depending on the amount of memory/complexity of checks. It certainly looks a very useful utility.

Thanks again,
Tim.

[retromit]

Sounds like a good first step. Thanks Colin.

Tim.

Originally Posted by ScottishColin

I would replace the belts as a matter of course. They're very old now. Just search for 1530 C2N belt on eBay and you should find them cheap enough


Colin

[ajgriff]

Originally Posted by retromit

I'm hoping to get mine tested tomorrow and see if it will load anything. Jumping the gun a little, but what did you find as the main issues?

Anything I should check before plugging into the PET/loading for the first time?

As Sirius and Colin have said you'll almost certainly need a new drive belt. There is only one belt in your version of the datasette. I got mine here:

https://www.ebay.co.uk/itm/301304228...UAAOSwo~9hFTnY

I can only reiterate in capital letters the warning from Sirius: DO NOT HOT PLUG THE DATASETTE. Always switch off the PET before connecting or disconnecting any peripherals. I may well have accidentally blown a PIA by being careless.

Apart from the belt and repairs to a damaged case my datasette needed the following attention:

1. Replacement of a failed LM358 chip.

2. The auto-stop mechanism didn't work because of dried/hardened lubrication.

Note that the boards vary in black datasettes. The circuits are essentially the same but different PCB layouts and ICs are sometimes used depending on the manufacturer supplying Commodore at the time. We'll need to match up your machine to the documentation if you encounter electronic problems. The 'scope could come in handy too.

Finally both the datasette interfaces (J3 & J6) will only work fully with a working PIA in the UC7 socket.

Alan

PS Forgot to mention that I had to re-align the tape heads as well because a 'twiddler' had been at work.

[ajgriff]

Another thing that might be worth a mention is that I initially had trouble with the datasette not always reading and writing at the first attempt. This came down to oxidation of the board's interface conections so it's not a bad idea to give them a thorough clean. A going over with a soft pencil rubber and contact cleaner or IPA is my preferred method.

Alan

[ScottishColin]

I'm lucky enough to have two working datasettes so I could test with both of them plugged in. I found that the board connection on the inside of the PET (port 2) didn't work until I cleaned the board (gently) as per the post above.

Colin.

[retromit]

Thanks all for the advice. The new belt is now ordered, so when it arrives I can service the tape drive and see if it's able to load anything.

Just as an update; I've been running the daver2 EPROM SiriusHardware sent and everything looks fine. All the keys on the keyboard work okay bar one (the left shift key). All the memory tests pass, and I let it cycle round for 14 test passes with no issues. So this was reassuring along with the results from the memory tester earlier. Only one thing seemed to differ from the manual and that was the VDU test; it seemed to go straight to the keyboard, then memory tests. I'm presuming all is okay, but just a bit different.

I also ran the Slothie EPROM as well and, again, all looks good from that as well.

So I'm really just now waiting for the new PIA and belt. In the meantime I'll start to clean up the connectors as recommended by Colin and Alan.

Going forward, is there any advice or recommendations for any maintenance work to carry out on the main board? I've noticed a few of the PROMs get quite hot. Has anyone put heatsinks on these, or are they not really required? The electrolytic capacitors all look okay (no bulges), but I'm not too keen on replacing them if everything is working (if it's not broken...). Just wondering if anyone had any thoughts?

Tim.

[ScottishColin]

My keyboard was a right old mess with broken traces and keys not working. I fixed the traces with a bit of careful soldering. I fixed the keys by taking it all apart (there was a large amount of decades old crud in there including Christmas tree fir-tree pins), then carefully rubbing a sheet of printer paper gently on the keyboard PCB and the offending key's base that makes the connection on the keyboard PCB.

Hope this makes sense. If you do it, do it carefully.

This is a very useful video on how to take the keyboard apart - take a look.

https://youtu.be/xkoVVbdky_o

Colin.

[SiriusHardware]

I'm not sure but I think the Daver2 test code only loiters on the screen RAM test if a one-off write-read test of all the screen locations fails. Otherwise it continues to the other tests.

Not everyone will agree with me but I would say Tim, don't push your luck at the moment. You almost have that machine working now, doing anything unnecessary runs the risk of introducing faults you don't currently have - in particular, replacing caps without an actual reason to do so.

Get all the definite faults fixed and then run it for a few weeks until you are sure it is completely stable, and if you still want to do some maintenance or mods on it at that point you will at least be sure you are starting with a working machine. You may yet find you have to repair the IEEE port before you can connect something like an SD2PET to it.

PROMs running hot is just a consequence of the type of technology used in them, it was just tolerated as a fact of electronic life back in the day - heatsinks are one possible thing you could consider, or alternatively clone all the PROMs into equivalent EPROMs which won't run so hot and keep the original PROMs stored in a safe, dry place. This would require you to have some TMS2532s for the replacement of UD6, UD7 and UD9, and the means to program them.

For the key / keyboard problems, Colin is your native guide there as he has actual experience, having had to repair several different types of faults on his own keyboard. It does sound as though you only have one key offline, so it could be worse.

[SiriusHardware]

Tim also asked if he should continue using the UD5 (Basic Toolkit) PROM following on from its successful pin graft - I don't see why not, unless the running temperature alarms you.

[retromit]

Originally Posted by ScottishColin

My keyboard was a right old mess with broken traces and keys not working. I fixed the traces with a bit of careful soldering. I fixed the keys by taking it all apart (there was a large amount of decades old crud in there including Christmas tree fir-tree pins), then carefully rubbing a sheet of printer paper gently on the keyboard PCB and the offending key's base that makes the connection on the keyboard PCB.

Hope this makes sense. If you do it, do it carefully.

This is a very useful video on how to take the keyboard apart - take a look.

https://youtu.be/xkoVVbdky_o

Colin.

Thanks for the link, Colin. It looks like I've been pretty lucky with regards to only have one key issue. I'll have a look over the video, then see what could be the problem for the shift key.

Tim.

[retromit]

Originally Posted by SiriusHardware

I'm not sure but I think the Daver2 test code only loiters on the screen RAM test if a one-off write-read test of all the screen locations fails. Otherwise it continues to the other tests.

Not everyone will agree with me but I would say Tim, don't push your luck at the moment. You almost have that machine working now, doing anything unnecessary runs the risk of introducing faults you don't currently have - in particular, replacing caps without an actual reason to do so.

Get all the definite faults fixed and then run it for a few weeks until you are sure it is completely stable, and if you still want to do some maintenance or mods on it at that point you will at least be sure you are starting with a working machine. You may yet find you have to repair the IEEE port before you can connect something like an SD2PET to it.

PROMs running hot is just a consequence of the type of technology used in them, it was just tolerated as a fact of electronic life back in the day - heatsinks are one possible thing you could consider, or alternatively clone all the PROMs into equivalent EPROMs which won't run so hot and keep the original PROMs stored in a safe, dry place. This would require you to have some TMS2532s for the replacement of UD6, UD7 and UD9, and the means to program them.

For the key / keyboard problems, Colin is your native guide there as he has actual experience, having had to repair several different types of faults on his own keyboard. It does sound as though you only have one key offline, so it could be worse.

Yes, I totally agree with just getting everything on the PET working. I'm not a bit fan of chaning things just for the sake of it. I've seen far too many videos where people just seem to charge into things, then wonder why things go wrong! I was maybe jumping the gun slightly by asking if there was any advice for long term maintenance.

That sounds a good idea of replacing the main PROMs with EPROMs. At least that would keep the original PROMs safe, just in case there was an issue. Might be something to look into.

In the meantime, I've just been cycling the test PROMs you created for me, and the results look good. Fingers crossed the new PIA and cassette belt arrive this week, then it would be good to get something loaded/running on the PET.

Tim.