Loud humming problems

[noise control]

Hiya Guys, I need help to fix 2 small practice amps and a stereo amp which my brother and I broke while trying to shatter a glass with a software based tone generator. Yeah I know, pretty stupid, but we were drunk. Anyway they all now have the same problem, they just hum loudly when switched on. Adjusting volume makes no difference and guitar plugged in makes no sound. I am sure it is probably a simple problem and any help would be greatly appreciated. Thanks, Dave.   

[R.G.]

Unfortunately, that may not be a simple problem.

I'm guessing that the procedure went like this:
- turn up the amp medium loud
- turn on the signal generator
- wobble around the signal generator until the glass seemed to be vibrating
- then turn up the amp as loud as it would go and wait for the glass to shatter
- when that didn't happen, turn up the software tone generator to as loud as it would go and wait for the glass to shatter.

That's also a medium-good procedure to kill small amps, btw.

There's no good way to guess at the cause from this amount of information. I find it odd that they are all just humming loudly, same symptom, neither of them dead silent or with popped fuses.

Take your voltmeter and measure for DC voltage on the signal output of the amps. I'm guessing that there will be a significant amount of DC there, indicating blown output devices. If the outputs are within 100mV of ground, it's likely the front ends that are dead.

Can't tell more than that without more info.

[Enzo]

I'm with RG here.  You probably blew the output stages of the amp.  When you flip it on, look at the speaker cone.   Does it move one direction and stay there?  That would mean DC on the output.  If your practice amps are common, there will be a five-legged power amp IC on the heat sink, and it will have died.  Number like TDA2040 on it.

[joecool85]

As always, R.G. and Enzo, you guys are spot on as far as I can tell.

Also, neat idea breaking a glass with an amp and a tone generator...might take a bit (a lot) more wattage though...and ear plugs.

[noise control]

Thanks guys, the Peavey I have has that TDA2040 IC in it. I desoldered it and will find a replacement. I'll let u know how it works. Once again thanks for the help.