Sony fh-e828 amp fix

[angibanjy]

I know this might not be the right place to write this but I'll do it anyway. 

I have a Sony fh-e828 amp, and recently it stopped outputting sound to my bookshelf speakers. So I tried to open it and i saw that something was shorted near what seamed to be the protection circuit. I tried to probe the output to see if that was the problem and just as I speculated there was no AC current going trough, thus no audio output. 

What I want to know is what do i do know?

[H713]

Few questions:

 

1) Does the speaker protect relay pull in when you power it up (assuming it has one)? If not, this is either a problem with the protection circuit (less likely) or a problem with the amplifier circuit (more likely). If you determine that this relay is not engaging, then you'll want to probe the output of the power amplifier circuit. This is NOT the same as the speaker jacks (which come after the protection circuit). Anything up to a few hundred millivolts of DC is probably OK, but if you're seeing several volts (or if you're seeing something like 30 volts), then something has failed in the amplifier, and the protect circuit did its job (and saved the speakers from destruction).

 

2) What did you find that was "shorted"? 

 

3) Are you getting sound out through one of the two channels, or neither?

 

4) Are there any blown fuses?

 

It looks like service manuals are available for this amplifier. Until you have that in your hand, you're sort of shooting blind. What I have stated so far is based off my knowledge of how most amplifiers are built, so some of it may be irrelevant for this particular device- I have not looked at a schematic for one.

FWIW, AudioKarma or DiyAudio are better discussion boards for troubleshooting power amplifiers. There are VERY few people on the LTT forum (or any major tech forum, for that matter) who are any good at troubleshooting analog electronics. DiyAudio, on the other hand, has a lot of real analog geniuses, including some very well-respected design engineers. 

Edited March 8, 2021 by H713
Clarification.

[angibanjy]

1) nothing happens

2) two little connections near the protection relay

3) neither work

4)There are 2 fuses i can see, i probed them both and they are not blown.

Thanks anyway  

[H713]

Can you elaborate on what "two little connections near the protection relay" are? That could refer to about 100 different things, any of which may or may not be a problem.