PET 8032....DEAD

[cbmeeks]

Sometimes, life just kicks you in the teeth.

After all this talk I've had on this forum about bringing out my beloved PET 8032, it is no more.

Well, I'm being a little dramatic here. Anyway, here's what happened.

I removed all of the custom work that had been done to the PCB and went back to stock. I haven't actually recapped the PCB yet. After talking about it in the other thread, I thought I would take a chance and just see if it still worked. So I plugged it back up and turned it on.

Monitor lights up and the image is a clear as the day it was made. Absolutely SHARP picture at 80 columns. I sometimes forget what a good monitor that was designed for 80 columns can do.

So I'm absolutely thrilled. I've been writing some BASIC programs for the last 20 minutes and it's working great.

Then, it happened. I heard some "sizzling" and then a pop. When I realized what I heard I jumped up and killed the power to it. That's when I saw smoke come out of the back of the monitor. Now the whole downstairs stinks. lol

What's weird is that I never actually saw the screen go off! It's like it would have kept working but I didn't take any chances. I would have assumed the picture gone out instantly.

Also, the PCB seems to be fine. Nothing is hot. The giant capacitor I've been talking about looks good and is cool to the touch. So I think something fried on the CRT itself or on the analog board for the CRT.

I know there are some high voltages in that CRT so I'm not going to touch it. I've disconnected the PCB from the power supply. And I'm going to put a note inside reminding me to NOT plug it in until it is repaired.

So, I'm a little bummed out about it. I've worked this entire weekend cleaning this thing up. Ugh.

On the positive side, I think the PCB would probably be OK. Also, there are a couple of places in town that work on plasma TV's so they might also fix CRT's. So I might take it by there and see if they could fix it.

Anyway, that's my depressing news for the night. :-/

[jim30109]

That isn't unusual with vintage gear being powered up. On the bright side, you were there. I've heard stories of people bringing up old gear and leaving it unattended with some nasty results.

Capacitors tend to be the most common failure, but it could be a lot of things. Hopefully it is something you can get a replacement for--restoring vintage gear of any type gets frustrating when it is a custom or hard to find component.

Good luck with it!

Jim

[BigDumbDinosaur]

cbmeeks wrote:

Sometimes, life just kicks you in the teeth...So I think something fried on the CRT itself or on the analog board for the CRT.

Smells like the monitor's flyback transformer may have gone south. Unfortunately, that seems to be a common sort of failure in elderly video gear, and sometimes it's caused by nothing more than the coating of dust that has collected on all the high voltage parts. I've had quite a few WYSE 60 terminals eat the flyback and make lots of vile-smelling smoke in the process. Carrying out a repair may be a challenge, primarily in tracking down a replacement flyback.

On occasion, a failed flyback will take some horizontal sweep circuit components with it. I don't want to sound like gloom and doom, but you should be prepared.

[Dr Jefyll]

cbmeeks wrote:

What's weird is that I never actually saw the screen go off! It's like it would have kept working but I didn't take any chances. I would have assumed the picture gone out instantly.

It wouldn't surprise me if you CAN just keep working. Plug 'er in and turn 'er on -- that'll settle the matter! I get that you prefer to be cautious, however. Or at least let the smoke clear!

Based on what you said, it certainly doesn't sound as if the flyback or the sweep circuit is affected. Whatever went pop is something not actually essential for operation, or at least not essential for what you were doing at the time. (It may seem weird, but it's really not.) The sizzle and pop suggest to me that an electrolytic cap failed, but I could be wrong.

Edit:

cbmeeks wrote:

there are a couple of places in town that work on plasma TV's so they might also fix CRT's. So I might take it by there and see if they could fix it.

Anyway, that's my depressing news for the night. :-/

Are you not able to locate the popped part visually? It may be a simple matter to replace it. Maybe in the morning this whole situation will seem brighter. Keep us posted

[Tor]

BigDumbDinosaur wrote:

Smells like the monitor's flyback transformer may have gone south. Unfortunately, that seems to be a common sort of failure in elderly video gear, and sometimes it's caused by nothing more than the coating of dust that has collected on all the high voltage parts.

That was the most common reason for TVs catching fire, back in the CRT days (my original education was TV repair, so I did a bit of that, even after I went into engineering and computers). Which is why yearly vacuuming (by someone who knows what they're doing) was recommended. Some never did, and many of those TVs would catch fire, sometimes with fatal results. A neighbour barely avoided a house fire by running the TV (which was on wheels) straight out the door an into the snow.

[BigEd]

Quote:

What's weird is that I never actually saw the screen go off! It's like it would have kept working but I didn't take any chances. I would have assumed the picture gone out instantly.

The ones in the Beeb which fail with smoke are not essential, but should be replaced. Could be the same situation. I share your fear of high voltages - I have a Vectrex which failed in that area, and I'm reluctant to investigate.

[cbmeeks]

Thanks everyone for the advice. My main concern with trying to troubleshoot the issue more are the high voltages and my lack of knowledge. I'm pretty good with a soldering iron and troubleshooting basic digital circuits but I'm nowhere near the level I should be to mess with that stuff.

However, this weekend I may take the top apart and see what I can see. If I see a capacitor that obviously popped then I might actually try to replace it. If so, I will post a lot of pictures and ask some advice before I do. Again...death by Commodore PET is not something that excites me. lol

Like Jim said above, it was good that I was actually there with it. One time I accidentally left my Commodore 1084S monitor running all night while I was in bed. Boy did I feel stupid after that. Fortunately, nothing happened. Normally, however, I don't ever leave vintage equipment running unattended and I almost always run them through a dedicated power strip that I can just turn off.