Electronics > Repair

Weird Channel Output Problem - Onkyo TX-SR 508

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I would definitely replace or bypass the relay first. This does seem like it could be caused by a bad relay contact.

Yes this is closing in on a relay or other weak contact in the output path (speaker output terminal solders are worth checking too).
Some relays are sealed and usually the most reliable, others can have the cover removed, list of the time it's more convenient to desolder the relay for that.
I clean relays with contact spray and a small piece of paper, I'll make a closed-contact resistance measurement before and after.

That doesn't look like a burn mark on the resistor just ambient dust / smoke accumulation due to hot components.

Another vote for speaker relay. I see them quite often. Cleaning can work if you can't find a good replacement, but do not use any abrasive on the contacts as it will remove the plating and just make it worse long term. We use the contact cleaning strips (Electrolube?) for this and it works well if we can't replace the relay because it's too weird.

Hello everyone!

I have some good news, the problem was indeed a bad contact in the relay of the rear surround channel. I also noticed that there was a difference in sound level on another channel. It was also a bad contact in the relay. I changed both relays with compatible models that I had. Unfortunately I could not clean them, as they are sealed (Thanks anyway for giving me your cleaning techniques, I am sure it will be useful).
The amp work like a charm now.

I took the opportunity to redo the soldering of the speaker output terminal card.

--- Quote from: slbender on December 03, 2022, 11:41:48 pm ---Those white things look like dual fusible emitter resistors (if the have 3 pins out the bottom) one side may be open. I have a 2 channel “Korea” made receiver with an open resistor on one side.  I’m going to replace with two 0.27 ohm/2 watt discrete parts. Not sure of each resistor’s power rating.  Measure center pin to either end, to see if there is an open. An open resistor usually will mean a blown transistor also, my set uses Sanken 2SB1560 / 2SD2390 flatpak darlingtons, beta usually measures ~68 - 210, best if a matched pair.


--- End quote ---

You are right! There are 3 pins on the bottom. If I remember correctly, I had tested them and I didn't find any anomaly. The power is 2 watts per resistor i think, according to the service manual. I have seen that some people replace them with two resistors as you are about to do.

--- Quote from: shakalnokturn on December 09, 2022, 08:57:14 am ---That doesn't look like a burn mark on the resistor just ambient dust / smoke accumulation due to hot components.

--- End quote ---

i don't know what this is, I've tried to cleaned it but i wasn't able to get ride of it. But the resistor is fine ! l’m happy with that.

Thanks a lot for all your answers !  :-+
Merry Christmas everyone  ;D


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