WPC sound board blown capacitors

[DSB]

I'm helping a mate get a Fish Tales going after it has been in storage for 10 or so years.

I have fixed or diagnosed most the problems but when the machine was plugged in several capacitors on the sound board blew up violently together (C28, C46 and C47). I haven't had much to do with sound boards so was curious to know if anyone has any helpful info.

Could it just be the old capacitors or could there be some problem elsewhere. A faulty regulator perhaps?

[robm]

He he. Always fun seeing the tantalum caps explode in fireballs! This happens when they dry out from sitting a few years. Replace all the 1uf tantalums and you should be right to go

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[robm]

Oh. And you can just use elctrolytic caps as replacements. Its a bit of a pain but you have to remove the 2 larger electro caps at the bottom of the board to replace 2 tantalums that are near the heatsinks

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[DSB]

Thanks Rob.

Quite spectacular. I saw them glow red and before I could switch her off I heard pieces of capacitor hit a wall 5 metres in front of the machine!

I am hoping it is just the old caps.

[robm]

Yeah, i have had 6 or 7 do it to me from a stash of old machines i picked up. Part of me says to replace them before i power an unknown board up but the other part says wait for the surprise fireworks if they happen!

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[DSB]

I have now replaced the 1uf caps as well as the other electrolytic caps on the board. It is now working with clear music and sound in game and in test mode. The only problem now is a small pop/crack/click when a ball is shot into the shooter lane(when the solenoid fires) and also when you enter and exit the menu. Not loud but doesn't sound right either as my working sound board does not do this in the same machine. I have noticed the amp chip runs slightly hotter than my working one if that means anything? I am in the process of checking all the tracks on the board which I worked on following the schematic. Any other suggestions would be appreciated. Thanks Dan

[DSB]

Found the trouble  Removed C18 but forgot to replace it! Seems louder than normal pops is a result of that.

[robm]

Yep c18 is related to volume control. I have had sound boards that are very loud and volume down to 0 does not decrease volume. Replace c18 and all works well

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[Wiked]

That's good to know Rob as my FT is very loud when turned on and reducing the volume does nothing. I will have a look at C18 now.