Hi guys I got this stereo unit the other day. It has 65 volts on the center pins of the current limiting resistors of both channels but both sets of transistors test good? Has anyone had a repeat failure in the feedback section on these? I tested all the transistors and diodes in the feedback section and didn't find any shorts. I also have another Sony amp (STR-DE625) with a similar issue (-46v) but it is only on the center channel on that one. I keep seeing references to the protection relays causing the problem but as I understand they simply remove the speakers from the circuit. I don't have too much experience with amps (fixed 5 so far) and these two Sony's are making me scratch my head. Any thoughts?
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Liberating magic smoke one part at a time -
Re: Sony STR-D365
Managed to get this up and running, ended up being a poor connection on the volume control board. I'm not sure why that was causing DC on the output? But its been up and running for the last couple hours. Hopefully it will lastLiberating magic smoke one part at a time -
Re: Sony STR-D365
It depends on the topology. An amp with no capacitors in the signal path sounds better, so some designs are fully DC coupled. So if there is something wrong anywhere in the DC coupled path, you will end up with that DC amplified at the output, which usually causes it to stick to one of the rails as you have found.A working TV? How boring!Originally posted by PeteS in CAComment
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Re: Sony STR-D365
It looks like the volume ctl circuit is dc blocked via c701,c751 so there may still be a bad connection in the amp section somewhere, time will tell if it acts up again. If there were bad connections on the volume board, I'l bet there are some on the amp board too.Last edited by R_J; 07-09-2015, 04:23 PM.Comment
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