SWR Workingman's 10 bass amp (C6 10UF exploded, TDA7294 partially melted))

[survivor]

Hey guys/gals,

My first post here. I have a '04 model Workingman's 10 and while playing it I heard a pop and the amp went completely silent (no sound at all through the speaker). Took the chassis out and the fuses are OK. I noticed that the cap marked with C6 (10UF) has exploded/vanished and the power amp IC attached to the heat sink U1 (TDA7294) has partially melted. CORRECTION: The IC is not actually melted but it is damaged due to the exploded C6 I guess, I found pieces from the black substance from it on the bottom of the cab.

Small additional detail: I was physically turning the amp to look at the back of it when it "popped".

What do you recommend me to correct the problem? I live in Atlanta, should I take the amp to a SWR tech (if available) or should I get new parts and try to fix the problem by myself? I can solder and read schematics. BTW I bought the amp used a few days ago and straightened some components on the PCB, C6 MAY have been one of the components I touched but I am not sure.

I can post photos if they would be of any help.

Adding: When the output switch is in the "phones only "position I hear only hum though the headphones. The other two positions are completely silent though phones too. I get the signal to headphones though effects send and tuner out jacks.

That vanished C6...is it 50V electrolyte as its neighbor C5 is?

All in all, should I simply get a new TDA7294V and C6 and turn the amp on to check if it works?

Thanks, in advance!!

PS: Partial schematic posted by acorcos in this thread:
http://music-electronics-forum.com/s...workingman%27s

[Enzo]

Yes, you TDA chip blew up, and C6 is indeed 50v.

[survivor]

Thanks Enzo. Are those caps at Radio Shack OK for C6?

I found some TDA7294V chips at good price here http://cgi.ebay.com/ws/eBayISAPI.dll...:X:AAQ:US:1123 I bet that "V" means vertical mounting for vertical heat sink so these should be OK I think.

The white grease stuff between the chip and heat sink must be for heat conductivity, do I need to buy that somewhere to add or do you think what is sticking in the heat sink will be enough?

Tks again.

[Enzo]

I have no idea what is at Radio Shack. if they have 10uf 50v caps, then they should be ok, but if all they have is 35v, don't.

Heat grease. never think up reasons not to do things right. Get some heat grease.

[survivor]

10-4. I'll get some thermal grease and make sure the cap will be rated for 50V. Would +/-20% tolerance be OK or should it be more accurate?

[Enzo]

20% will be just fine.

[survivor]

Thanks Enzo! Have a great weekend.