Sonic impact t amp - supply voltage on the output of one channel

[deiksac]

Hi, I have been tinkering with the little box a while ago but did not finish it. Got back to it yesterday evening and found out that there is full supply voltage present on both channels and lots of brum. Recchecked connection and managed to make one channel work properly but could't have made the other channel work properly.

Any idea for what might be the cause?

(list of mods - changed diodes for byv27-200 schottkys, shortened feedback path - moved r5 closer to the chip, bypassed volume pot and conected inputs directly to the board thru 2.2uF and 22kohm; also drilled the board where r4 and r5 are connected)

 

[Lostcause]

Funny you should have that problem, one of mine just did the same. I did a fair amount of modifications and think that I've damaged the chip...static maybe?
Anyway, after checking everything there is nothing left so it looks like toast!

Next board please!

Lee

 

[deiksac]

Well since I managed to make one channel operational, I believe the other one is not yet lost

 

[Lostcause]

Well since I managed to make one channel operational, I believe the other one is not yet lost

How did you revive it?

 

[DcibeL]

The only advice I can give is to read a thread I started here. My problem was eventually fixed by placing the coupling caps at the amp side of the pot. This is very important for their operation.

 

[Lostcause]

Wish it was that easy on mine!
This is the 3rd I've done and it has all the other 'experiments' lumped into one.
Think it's an AMP6 next....definately!

Lee

 

[deiksac]

Thanks a lot dCibel, I had the other input shorted. Anyway I screwd some other thing when desoldering broken LED leads so now the situation is just reversed and there is no more short on either input. I am quite curious whether I can make it work again