Fender Rumble no output

[Tone Meister]

Pro bass guy plugs in his uber-powerful Steinburger bass into the Rumble 75. Says it started "fizzling, then died."

1. Amp powers on
2. Speaker is good
3. LINE OUT works into a second amp
4. 1.5VDC on speaker output
5. Tried both inputs
6. HEAD PHONES output works into a second amp

I realize this could possibly be the mute circuit in the TDA7294, so I'd like some help sorting this out. Thanks in advance.

[Tone Meister]

OK, U6 TDA7294 and the .1 C333 are smoked.

Should U3 TDA7294 and .1 C20 be changed at the same time?

Should I look for a cause, or are these considered normal parts failures?

[The Dude]

I wouldn't say "normal", but output devices are often first to go in any amp. Causes might be shorted speaker cables, output impedance too low, amp driven too hard for too long, etc.

The TDA's in this amp both drive the same speaker, so it might not hurt to replace both. They would have shared current. It's easy enough to check the caps. If you do replace just the one IC, bring the amp up slowly on a variac and monitor current or use a light bulb limiter. I always do that anyway when first powering a repaired amp. Only hook up a speaker after you verify no DC on the output.