Commodore PET 2001 voltage regulators

[ScottishColin]

I have a spare sticker which I think is left over from inside the monitor. You couldn't do me a favour and photograph the stickers inside the monitor case could you? I should have been paying more attention...

Colin.

Originally Posted by retromit

I think for the case, I'm more inclined to leave it as it is (providing it doesn't get any worse). Give it a really good clean and maybe treat some of the small areas with white vinegar, but nothing else. The case itself has a few battlescars, but I don't really want to do anything that I don't need to.

That's a good call about the rust in the monitor, and thanks for the information. I'll be very honest and say I really don't fancy discharging the CRT, and removing everything but if it's what I need to do, then I may have to do it. It's certainly the area with the most rust, and not easy to clean at all.

Tim.

[Mark1960]

I’d also recommend a phosphoric acid rust remover to remove some of the rust and neutralise the rest. It might also be worth cleaning with t-cut, rust spots tend to stain the surface of the paint over a larger area than the rust itself. Both should be available from a local car accessory shop.

[ajgriff]

Originally Posted by SiriusHardware

....... the idea of having the PCB assembly whanging about near the tube neck while attempting to carry out fairly heavy physical work on the inside of the monitor casing makes me wince, to be honest.

Fair comment but I was only thinking in terms of lightly brushing on the rust killer and wiping it away a few times with a wetted cloth after the allottted time.

Alan

[ajgriff]

Originally Posted by ScottishColin

Oh - and removing the CRT and the board from inside the minitor shell isn't for the faint hearted either.

Agreed. I chickened out of dismantling the monitor for the purposes of giving everything a good clean when I couldn't easily undo the clamp screws securing the CRT. Too much risk of a ruined CRT. I take my hat off to Colin.

Alan

[ajgriff]

Originally Posted by ajgriff

Just for fun I've attached an image taken from the web showing how not to do the respray. Looks like woodchip wallpaper. No idea how it was done but a smooth gloss finish would have looked much better in my view.

I've been idly musing over how the woodchip effect was achieved. Looking closely at the photo (post #318) the finish appears to be quite thick, almost gloopy, which could be indicative of powder coating. It's possible that the powder coater wasn't too sure about what they were trying to achieve and used much too coarse an additive in the mix. I wouldn't have been a happy customer whatever the cause.

It'll be interesting to see how Tim approaches the rust issue. Last step in a very worthwhile journey.

Just a quick update on the progress of my Chinese chips (aka MC3446s) which have been allocated a SpeedPAK tracking number but are not yet shown as being in transit. Estimated delivery date 24th Nov to 2nd Dec.

Alan

[Slothie]

I seem to recall the texture on my (early) pet looked like the picture, but maybe it was a little finer-grained. I know the later PETs with plastic panels were much flatter in finish because I also have a 3032 with the plastic case and this was something I noticed.

[ajgriff]

Am I right in remembering that you haven't seen your PET for a while Slothie? If my 2001-8 is anything to go by the finish is nowhere near as heavily textured as the woodchip version but who knows what went on in the office furniture factory. Anyway enough of this digression as I've already spent far too much time typing forum posts today.

Alan

[Slothie]

Originally Posted by ajgriff

Am I right in remembering that you haven't seen your PET for a while Slothie? If my 2001-8 is anything to go by the finish is nowhere near as heavily textured as the woodchip version but who knows what went on in the office furniture factory. Anyway enough of this digression as I've already spent far too much time typing forum posts today.

Alan

Yes, its been a couple of years. I hope to get things back soon! Mine was manufactured int he US and imported to the UK, so its possible the finish was different too. However, I did say the finish may have been a little finer than the "woodchip" picture, although it looked very reminicent. I do remember however how much effort it took to get marks off the paint because of the texturing.

[ajgriff]

I imagine all the early chiclet machines were US imports. Mine certainly says 'Made in the USA' on the serial number label. Here I go again. Time to shut down the tablet.

Alan

[SiriusHardware]

I've never owned or used one of these and I'm not really in the market for one but if one fell into my lap, I would be be so disappointed if it turned out to be in working order.

The available information is so comprehensive and so complete that it makes them a real pleasure to work on, even from a distance.

[TonyDuell]

To be fair that applies to a lot of computers from that sort of period

Back at the time I was a TRS-80 user, not PET. But there were/are full technical and service manuals with circuit diagrams, theory-of-operation, etc sections freely available for all the TRS-80 machines and peripherals.

And look at the DEC PDP8 and PDP11 manuals for the TTL-based machines at least. A manual of circuit diagrams. A manual of how it works at component level. A manual of exploded diagrams and parts lists. And so on. Yes, the manuals just for the CPU take up quite a bit of shelf space, but you can read how it all works.

[ajgriff]

Originally Posted by SiriusHardware

I've never owned or used one of these and I'm not really in the market for one but if one fell into my lap, I would be be so disappointed if it turned out to be in working order.

Oh go on Sirius you know you'd like one really. Trouble is at the rate you're going there won't be many non-workers left.

Alan

[ScottishColin]

I'm waiting for the next one to turn up on here. There's a good team of fixers now.

Colin.

Originally Posted by ajgriff

Oh go on Sirius you know you'd like one really. Trouble is at the rate you're going there won't be many non-workers left.

Alan

[SiriusHardware]

I have to say that Daver2 (author of one of the PET test EPROMs we have been grateful to have the use of) has been 'doing' epic PET repair threads over on the Vintage Computer Forums for a lot longer than we have here.

It's possible that he is also a member here but he obviously likes where he is, and let's be honest, the VCFED forum is a more logical place to conduct that type of thread.

But as Colin said, we have gathered quite a good little group of PET owner / drivers and other interested individuals here with a fair bit of actual, practical and technical experience between us, and most of all we take as much time and work at whatever level the OP needs us to, as long as the OP is able to work patiently and methodically and report results back.

My growing impression is that PETs in particular naturally seem to attract that sort of person, which greatly increases the chance of a successful outcome.

[retromit]

Originally Posted by ScottishColin

I have a spare sticker which I think is left over from inside the monitor. You couldn't do me a favour and photograph the stickers inside the monitor case could you? I should have been paying more attention...

Colin.

Here's a couple of pictures of the stickers. I'm not sure the orange sticker is in its original spot, but seems pretty stuck in place.

Tim.

[retromit]

I've been doing some more cleaning today, and it looks like most of the surface rust spots could be staining. I've attached a picture after cleaning (should really have taken one before!), but it show a couple of very small marks.

I think I'll continue with this and give the case a really good clean and then see how everything looks. I may have been a bit too critical, but after the cleaning so far, the case doesn't look too bad as most spots seem to be coming off. It could be the T-Cut which was recommended may also be something to try. I certainly don't think a respray is required for the main casing (nor monitor (outer) case).

However, I don't think I'll be able to get away with that on the inside of the monitor casing. I tried a light scrub near the back, and it's quite rough; so I think it will need some chemical help. It looks to just be the bottom of the casing (as the sides/top look clean), but something will need to be done.

So I think I may yet ahve to look at removing the monitor casing from the main casing, then trying to remove the PCB/CRT. I'm not looking forward to this!

Tim.

[ScottishColin]

That's great - thanks very much. Gives me a good idea where to put mine back.

I'm guessing it's the initials of the person qho QC'ed the monitor PCB, but I can't be sure.

Colin.

Originally Posted by retromit

Here's a couple of pictures of the stickers. I'm not sure the orange sticker is in its original spot, but seems pretty stuck in place.

Tim.

[ScottishColin]

Getting the monitor case off the PET case is easy - undo four nuts inside the PET Motherboard case at the top. Make a note (photograph) of any cables before you unplug them; you'll have to unplug the monitor cable from the motherboard at least.

And please look up discharging CRTs before you go any futher. Even if you're not planning on touching the CRT, you might do so by accident. Here's my discharging tool, and also a couple of videos that are worth watching.

https://www.youtube.com/watch?v=x1DeMOl_nK4

https://www.youtube.com/watch?v=mParOYnZ3Fw

If you go through the thread for my PET work, start at post 1767 (!) for all the helpful advice I was given.

Colin.

Originally Posted by retromit

I've been doing some more cleaning today, and it looks like most of the surface rust spots could be staining. I've attached a picture after cleaning (should really have taken one before!), but it show a couple of very small marks.

I think I'll continue with this and give the case a really good clean and then see how everything looks. I may have been a bit too critical, but after the cleaning so far, the case doesn't look too bad as most spots seem to be coming off. It could be the T-Cut which was recommended may also be something to try. I certainly don't think a respray is required for the main casing (nor monitor (outer) case).

However, I don't think I'll be able to get away with that on the inside of the monitor casing. I tried a light scrub near the back, and it's quite rough; so I think it will need some chemical help. It looks to just be the bottom of the casing (as the sides/top look clean), but something will need to be done.

So I think I may yet ahve to look at removing the monitor casing from the main casing, then trying to remove the PCB/CRT. I'm not looking forward to this!

Tim.

[SiriusHardware]

Although the tube voltage (thousands of stored volts) sounds fearsome, if you are unlucky to make contact with it it will just feel like a nasty static shock. You are more likely to hurt yourself physically by trying to whip your hand away across sharp bits on the PCB or chassis.

The real danger is to other components in the machine - if the earth clip slips off and goes on a wander across the circuit board at the very moment you make contact with the high voltage then the tube will discharge into whatever the clip happens to be dangling next to at the time, so I can't stress enough, the earth end of the discharger must be absolutely securely connected to the earthy part of the tube with no possibility that it will slip off while you are attempting to discharge the tube.

[retromit]

Originally Posted by ScottishColin

Getting the monitor case off the PET case is easy - undo four nuts inside the PET Motherboard case at the top. Make a note (photograph) of any cables before you unplug them; you'll have to unplug the monitor cable from the motherboard at least.

And please look up discharging CRTs before you go any futher. Even if you're not planning on touching the CRT, you might do so by accident. Here's my discharging tool, and also a couple of videos that are worth watching.

https://www.youtube.com/watch?v=x1DeMOl_nK4

https://www.youtube.com/watch?v=mParOYnZ3Fw

If you go through the thread for my PET work, start at post 1767 (!) for all the helpful advice I was given.

Colin.

Thanks for the links and details, Colin. I'll certainly have a look over those to see what's involved. I think this will be a weekend job so I've plenty of time to go through through everything, making sure all is safe, then cleaning the rust.

Regarding the aligator clip. Is there a recommended earth point on the PET, or do you use one near the CRT?

Tim.