Sony TA-V3 Amp

[dirtyhanfri]

Hi

I got this amp for free, not working propperly, it plays, sounds nice, but suddenly the speakers start peaking, sounds like DC peaks hitting hard the speakers, I'm scared about my woofers. It happens with every input, in both speakers outputs. The amp looks like working fine except for that, so I think it wouldn't be hard to fix it. Never tried to repair a power amp, some basic safety tips or things I should be aware of? Also, any idea on where start looking?

I've downloaded the manual service, with the schematics and such.

Some pics of the unit:

Front:

Back:

Inside:

The IC:

Main Board:

Fabricado En España (Made In Spain) Maybe that's the main issue with it?  ;D

Input Board:

Power Transformer

Would be nice to make it work, if it ain't worth, always could recycle the case for a little project I'd like to do...

EDIT: Maybe I should say I've sprayed contact cleaner (the same I used in my mackie) in the volume fader when it was working, some time ago, and then it keeped working for a few months.

 

[PRR]

Put the DC volt meter on the speaker outputs. Is there real DC there?

One way that power-amps die is a dead-short to the power rail. 30 Volts DC on the speaker is bad.

"Good" hi-fi of medium/large power often have a DC detector. If the voltage is all one-way for more than a part-second, they cut-out a relay to protect the speaker. You can usually hear this.

I've had trouble with a phono preamp into a large Sony. The (external) preamp had quite extended subsonic response. Turntable rumble 1Hz-10Hz looks enough like DC that the cut-out would trip well before the system reached realistic level. (This was a piano studio, with classic performance on LP and two fine grands in the room; it would not play as loud as an actual piano.)