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soundstream px2.200 left channel audio distortion
soundstream px2.200 left channel audio distortion
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Old 5th December 2017, 01:56 PM   #1
paras is offline paras
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Join Date: Feb 2011
Default soundstream px2.200 left channel audio distortion

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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Old 5th December 2017, 04:18 PM   #2
jacampb2 is offline jacampb2  United States
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Location: Beaverton, Mi 48612
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
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Old 5th December 2017, 04:27 PM   #3
paras is offline paras
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Join Date: Feb 2011
hi Jason ,
thank you for your reply .
i have already tried it. cleaned the pots and switch with WD40 spray.
but problem remains the same .
no heating no sparks only output with crapy distortion.
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Old 5th December 2017, 06:25 PM   #4
jacampb2 is offline jacampb2  United States
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Location: Beaverton, Mi 48612
So cycling the pots does nothing, or does it have some impact on the level and or sound of the distortion? There absolutely could be bigger issues, but this is really common in older amps I've seen it a lot in Phoenix Gold and SoundStream. Do your op amps all have their +/- 15v (and 12v) rails?

Good luck,
Jason
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Old 6th December 2017, 02:38 AM   #5
paras is offline paras
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Join Date: Feb 2011
hi jason,
all rails are ok. today i will try desolder the pots and then rectify if pot is issue or not.
what about 5 ics njm4558l ???
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Old 6th December 2017, 02:41 AM   #6
paras is offline paras
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one more thing to mention is random voltage ranging from 0.23v to 8.79volts/sec is on output in left channel while ther is no input to the system.

while right channel remains 0.00volt
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Old 6th December 2017, 12:04 PM   #7
jacampb2 is offline jacampb2  United States
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Join Date: Aug 2007
Location: Beaverton, Mi 48612
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
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Old 8th December 2017, 03:45 AM   #8
Perry Babin is offline Perry Babin  United States
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Location: Louisiana
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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Old 11th December 2017, 05:08 PM   #9
paras is offline paras
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Join Date: Feb 2011
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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