Ampeg SVT-4 Pro

[melvin]

I have before me an SVT-4 with 5.6 volts of DC on the output of amp A. On the main board (pg 1, top right) R118 is obviously fried, R119 measures almost 1 meg (not visibly, but cooked?) and Q102 is shorted between emitter and collector. Is there anything else I should check or replace as a matter of course before I power it up again?

Thanks for any help.

[melvin]

I got the parts and installed them. I went ahead and replaced Q103 as well, although it doesn't test bad. I am assuming that's where all the current went when things got fried, but I'm not sure. It would be great if I got a second opinion. It would be sad if the same components fried again.

[Jazz P Bass]

If Q102 was a random failure, you may be ok.
To quote Enzo "Never come up with a reason to Not check something."
Taken another way, check everything.
These are some powerful amps, so I hope you have a lamp limiter, just in case you missed something.

[melvin]

Thanks for the reply. I do have a limiter. Another Enzo paraphrase is 'follow the current-whatever is downstream is suspect'. Did I get that right?

[Enzo]

Close enough. However I say it, it boils down to the excess current of whatever failure has to flow somewhere, so check everything in its path.