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Old 1st February 2003, 04:05 PM   #1
supes is offline supes  United States
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Default sony amp problem

hi, I have a 10-year old sony amp that I've been having some problems with lately. the problem is that my left channel really distorts the low bass notes, even at low volumes. the right channel is fine, and I've tested 2 different sets of speakers so I'm sure it's the amp. I have moderate soldering ability, is there any way I'd be able to troubleshoot and fix this myself? Anyone have an idea what the problem could be? Thanks for the help.
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Old 1st February 2003, 05:07 PM   #2
Netlist is offline Netlist  Belgium
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Hi Supes

We don't know the type of amp you have, so we can't tell you very much. If the amp doesn't have seperate PSU's for each channel, the PSU will probely be ok. Look for bad caps in the bad channel, measure the idle current and first of all, look for bad solder joints.

Hugo
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Old 1st February 2003, 07:11 PM   #3
supes is offline supes  United States
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sorry, the amp is a STR-D790 model. here are a few pics with the cover off:
http://members.cox.net/ksudar/amp.html

in the second pic, it looks like those are the transistors for the 2 channels. could you point me where to look for bad caps, and also how to tell if they're bad? also, how do I measure the idle current? thanks for the help.
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Old 1st February 2003, 08:09 PM   #4
Netlist is offline Netlist  Belgium
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Supes

I think that, without any experience on repairing amps like this, the chance that you succeed is rather small…but lets try!!

First thing to do is read Help on sony Amplifier . I don't know your particular amp very well, but if the heat sink temp is ok (should be slightly warm after 10') idle current will be ok too.

Take off the ground panel and DISCHARGE THE BIG CAPACITORS FIRST (the 8200µF) with a 50ohm resistor 5watts. Measure the voltage over the PSU caps BEFORE you attempt to solder anything! Shouldn’t be more than 1 or 2 volts. Redo every joint that looks suspicious carefully. Fire up the amp and listen…

I’ll be back tomorrow…unless i hear a big bang...with flares
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