soundstream px2.200 left channel audio distortion

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Hi friends,
i have unique issue with my soundstream picasso px2.200 amplifier. right channel is working superb but left channel has distortion of highest level even without input. left channel is playing but with same distortion frequency added to input freq.

i have checked all caps , transistors and mosfets
it uses d998 + b778 with ir44zn and st104ct and st104cta.
there is no sign of burn or so.

please according to experience u have, provide me with some solutions .
thanks in advance. attached image.
 

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I would try cycling the potentiometers several times and see if it makes any change. I have seen a lot of this style potentiometer causing similar issues. Unfortunately this type cannot be easily disassembled and cleaned. Contact cleaner sprayed in around the shaft and repeatedly cycling the pot may bring it back.

Good luck,
Jason
 
I'm kind of winging it here brother, I've worked on a lot of SoundStream stuff but not this amp. There are a whole lot better resources here then me, and hopefully they will give their thoughts shortly.

If the problem isn't due to something in the pre-amp stage, then my next thought would be that possibly the bias circuitry for the bad channel is malfunctioning. I wouldn't have thought it would cause the noise you are describing, but it's possible, especially if the bias current is drifting around.

Hopefully the others will speak up.

Good luck,
Jason
 
Amps that use boards like this are a nightmare. Every jumper that has solder top and bottom on one end of the jumper is suspect.

The best solution that I found was to desolder the jumper, top and bottom. Scrape the resistor lead or replace the resistor and insert a 1/8w resistor lead onto the hole, soldering ONLY on the top. Then on the bottom solder the other end of the resistor lead to some point on the trace leading to the pad on the bottom of the board. The second example is shown for top traces but it's only done on top where soldering to a point on bottom isn't feasible.
 

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Thank you all for shareing your experiance. i have replaced log potentiometers with new ones issue is so far diluted . now i have hiss sound coming from left channel while right channel is ok.

previously left channel was giving distorted output.... upto 12.67volts but now its minimised to 0.1 to 0.7 voltes random.

i day or two i will try changing switches n inform finally.
 
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