Looks like C26 and C28 have exploded pretty thoroughly. The scary thing is that those are just little filter caps across the amp power supply rails. There's not much that could explode those other than those rails going bad. Almost as if the supply on J501 ended up hugely too high voltage. The sound board should still run without those exploded caps,if there are no other faults, but something tells me that there's something else majorly wrong here, and the caps are just a symptom!

GI should be unrelated to the sound issue, unless something truly horrible has happened. WPC machines commonly have GI issues due to burnups on the GI connectors (bottom left of the power driver board, which I can't quite see in the photos). If your friend takes the display panel off, quite often blackened plugs can be found there, and the boards themselves often get damaged (burnt tracks, pins etc).

(Side note - I buy dead boards, so if you buy new replacements, I'd be keen to buy the old one(s)).

Given what I see there, yes, there's no way I'd be slotting a replacement in there before making sure that all the PSU voltages are healthy. Seeing the severity of the explosion there, I'd almost be considering 110v on the +/-12V transformer winding. I'd also expect that more than just those two caps are bad - it's fairly likely the regulators are blown as well, and maybe the amp ICs they supply. So you don't want to go exploding too many of these boards this way!

In addition - the fact that both rails have exploded strongly suggest bad voltage on the transformer connection. There's not much else that could cause that, as far as I can imagine. I guess it is possible that one or more of the bridge diodes (D1, 2, 3, 4) have shorted. That could do it, maybe.

Thoughts:
- Any hope of getting a measurement of the AC voltage across J501 pins 2 and 4 on the sound board? That would be an easy check as to whether it's safe just to replace the whole board.
- Are F501 and/or F502 blown?
- Voltage on connector J503, between pins 2 and 3, and pins 2 and 4? These should be close to -12V and 12V, but I doubt they will be.

The main reason I discounted this was because both the +12V and -12V caps went at once. That's not going to be a coincidence, surely? The only cause I can think of for that is the supply voltage going way high, or maybe the bridge rectifier failing in such a way that these ended up with reverse voltage on them...?

Also - if these went up on their own, I would have thought the sound would continue working fine, albeit with a bit of extra hash in the audio, perhaps (and some nasty black smoke). In the original post, he mentions sound stopped working entirely.

Would be nice if it was just a quick replacement of the caps. Re you repairing, he mentioned he needed a fix by next weekend - any hope of turning it around, including shipping both directions, before then?

Ah, well, if sound is still working, that's another thing entirely. Means that a bunch of things aren't fatally exploded, e.g. amp is OK, fuses aren't blown etc. So - maybe one of those caps blew ages ago, and all your friend saw was the second one go up in smoke completely on its own. If that's the case, you can just clip the old caps off the board and run it without them for the time being. Then perhaps you can sort it out yourself, or send the board to Chris for a tidy-up after the weekend, when there's more time. Chris - can you see any harm in running the board without those caps on the amp supply rails for a little while? They just look like HF smoothing caps to me, to keep nasty supply hash off the amp.

I think the best solution would be to pack the whole machine into a box and post it to me. I've been after a Funhouse for ages!

Here they are, in the red rectangles:

bangycaps.jpg

As Chris says, these amps need both a +12V and a -12V power supply. C26 (lower in the pic) and C28 (upper) do the same job as each other, one in the +12V supply, the other in the -12V supply. It seems a very unlikely coincidence that both would do a popcorn impression at the same time, but who knows. I suppose it is possible, if these caps weren't good quality. One of them could have gone off months or years ago, and all your friend saw was the other one following suit now. I know I'd be nervous about the whole situation though. It'd be worthwhile to replace them, and then measure the voltage across each one. It shouldn't be too far above 12V; less than 20V would be acceptable.

If everything's running OK, and there's no noticeable hum, things sound surprisingly healthy. If I were feeling particularly paranoid, I might replace the BR diodes (D1, 2, 3, 4) and the big smoothing caps (C24, C25). But really, I think you'd be seeing more problems than you are if any of those were really faulty.
The exploded components are 1uF tantalum caps (or were, in a previous life). Watch out for those if you buy a direct replacement, they're polarised. If you put them in backwards, they'll do the bang thing again.

Edit - buy high-rated caps to replace these! Maybe 30 or 50V.

There you go - I was trying to remember what the input rails ran on. Seems a bit mad, regulating that all the way down to 12V. Those regulators must run a bit warm. Oh well. Specing those capacitors at maybe 40V or higher would be a good idea then.

The 1uF tantalums can be found here:
https://www.greatplainselectronics.com/proddetail.asp?prod=CTA-1uF-35V

This is the 4700uF electrolytic:
https://www.greatplainselectronics.com/proddetail.asp?prod=CER-4700uF-35V
but it shows as out of stock. This would do, better specs:
https://www.greatplainselectronics.com/proddetail.asp?prod=CERH-4700uF-35V