PET 8032 not dead!!!

[cbmeeks]

About a year and a half ago (WOW time flies!), I reported that my PET 8032 went pop and let the magic smoke out.

I immediately powered it off (even though the CRT was still showing a picture). I looked all around and couldn't find anything substantial that was fried. Other than a potted inductor.


viewtopic.php?f=4&t=4586&hilit=pet+8032
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I never could find any debris anywhere and still don't know what fried.

So I said I would tackle later. Well, later finally came.

After reading a few comments about turning it on I thought what the heck. I plugged it up...kept my distance...and powered it on from a surge protector 6 feet away.

Low and behold....the damn thing works!

For those that said it was probably nothing important...well, looks like you were right!

I'm grinning ear to ear.

Let's hope it stays running for a long time. Now, time to have some fun with it.

(oh, and I will make sure not to leave the room with it plugged in)

[drogon]

I know nothing about the innards of PETs, however lots about the BBC Micro and the Apple II - the thing that frequently goes on these, and other computers of the era is the mains input filtering "X2" capacitors on the switched mode power supplies.

So have a look at the power supply (unplugged!) for what might look like a rectangular shaped capacitor that's cracked or shows signs of smoke damage.

They do work without them, but will inject noise down the power lies without it.

If it does look like that, then do some searching, there are a few places offering (e.g.) BBC Micro PSU replacement capacitor sets for the 3 main capacitors that are problematic there, however sourcing a new X2 capacitor is easy.

Cheers,

-Gordon

[Martin A]

If there is a blown X2, then you might want to consider replacing all of them.

Spotting the blown X2 in this PSU wasn't hard, but the state of the case on the other one in shot suggests it too wasn't going to last much longer.

The blown X2 isn't hard to spot !

[cbmeeks]

That's the thing...I cannot find it.

However, I admit, I haven't pulled the analog board out and looked super close. I've been avoiding that because the wires are soldered to the CRT. But, I think I can maneuver it out good enough to see it up close. I'll try to do that this weekend.

The PET is really great machine that doesn't get much love these days. I suspect because it is hard to collect for and hard to handle sometimes. I mean, it weighs a ton.

[Dr Jefyll]

cbmeeks wrote:

Low and behold....the damn thing works!

For those that said it was probably nothing important...well, looks like you were right!

Told ya. (The clue was when you said the picture didn't turn off after the sizzle and the smoke were noticed).

Quote:

I'm grinning ear to ear.

It's nice to hear you're once again able to enjoy the machine.

Quote:

(oh, and I will make sure not to leave the room with it plugged in)

Ironically, this machine is now less likely to go bang than your other PETs (and other misc. electronic appliances). The capacitor only dies once. And the other machines haven't had their turn yet.

Quote:

I haven't pulled the analog board out and looked super close.

The input filtering cap will be attached to the AC side of the switched mode power supply, or to the wiring that brings AC from the power cord to the SMPS.

-- Jeff

[Mike Naberezny]

cbmeeks wrote:

That's the thing...I cannot find it.

On the PET, the 3-prong AC socket has EMI/RFI filtering built into it. This can burn up. I don't have a photo of it but it looks similar to the one below. You'll have to remove the large transformer to see it clearly.

cbmeeks wrote:

(oh, and I will make sure not to leave the room with it plugged in)

One day, this AC socket burned up in one of my PETs. The PET was powered off but I was sitting near it working on something else. Suddenly, I heard arcing and smoke started billowing from behind the machine. I turned the power strip off immediately and it stopped. Since this experience, I never leave an older machine unattended while connected to AC. I either unplug it or have it plugged into a power strip that's switched off.

[BigDumbDinosaur]

Could be there was a spider inside her and sat down on the CRT's anode connection. That would definitely make a pop and some smoke.

[argonn]

I believe those sockets have Rifa caps inside (known for popping and releasing magic smoke). Experienced similar thing twice: first time with ancient CDD-521 CD burner, then with an old oscilloscope. After the smoke is gone the thing is working, except for capacitors having 0nF now. Fun