Hi everyone. I have just registerd to this forum hoping that someone can help me with a few tips. I don`t know if diyaudio.com is the right place for this but i`ll give it a try. A have just aquired an Onkyo TX-SV545 5.1 audio video reciever. It`s a pretty old model dating back to `99 but i kinda like it. My problem is that the reciever powers on, every switch every function works fine, the display is displaying everything that needs to be displayed but i have no sound. All of the 5 audio power stages are working perfectly, i have tested them with an externel audio signal. If i connect an audio source to any of the inputs except the 5.1 input, the rear speakers a working but at a very low volume. If i move te volume knob nothing happens only if it`s fully turned down then the sound stops, if i turn it up even just 1db the audio suddenly turns on like it`s a switch and no matter how far a turn it up the volume stayes the same. I now it`s not a diy amp, but the repair would be diy by me 😀 I really would like to fix this amp beacuse it would be a nice upgrade from my Yamaha A-960
If I was you I would check the boards for hairline cracks in case it has been dropped check for loose components,transistors ect... I use a toothbrush to poke around when its on, you can push down on the boards a bit while its on to check for cracks as well.Have a look at the ribbon connectors they can come loose.If it has the old style pots and switches(not digital) give them a clean and be sure to check for cold solder joints,If a solder joint doesn't look right resolder it by melting the joint and adding just a little bit more solder for the flux.Try that!
I have checked for cracks and bad solder joints and everything looks fine. A have pushed and poked the components and PCBs but nothing. It looks like that there is a probleme in the preamp stage, or some microcontroller. There are a lot of ICs, my guess would be that it has a major problem or something minor that just needs to be found. But what?
I would check your ICs that they are getting correct power for a start,download their datasheets and look for the typical power that they run at and what pins to measure. You will need a service manual to tell you as well.Check for discolored resistors bulging leaking capacitors,blown transistors,diodes,zener diodes ect... Do you have a DMM (Digital Multimeter)My advice is if you don't have much experience at fixing amps you'll be better off dicing it and getting one that works,honestly.
I have measured some of the opamps and the are all getting power as they should, however i dod not measure the controller ICs. I have a service manual but most parts are unreadable, i found it on google in pdf but it`s of poor quality. There are two 12v voltage regulators both of them positive and they are getting pretty hot, but they work fine and i have seen perfectly working amps with regulators that worked with the same temperatures. I have some experience in electronics, specially amps, but most of the audio gear I have repaired were vintage, the only modern gear i have repaired was a Panasonic mini Hi-Fi system but that only had bad solder joints. Another thing that i`ve found is thet the inputs are acting weird. No matter to what input i connect there is always sound regardless of input selection but only for the rears and in the same way with no control over volume and tone correction.
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