Check when that happens if you have an dc voltage going out to the speakers ... in normal operation volume at zero or when you have sound output ? To be sure the speaker protection systems is not triggering for nothing.
service manual : https://elektrotanya.com/onkyo_tx-nr636.pdf/download.html --- had to download twice, the first was zero bytes
The amps sections are bias adjustable .... thats nice ...
Dollars to doughnuts its a leaky muting transistor. Fairly common problem on most brands. Receiver goes to mute that channel while changing sources, thr trigger voltage to the base or gate of the transistor leaks through, DC ripples through to that channel's output.
Dollars to doughnuts its a leaky muting transistor. Fairly common problem on most brands. Receiver goes to mute that channel while changing sources, thr trigger voltage to the base or gate of the transistor leaks through, DC ripples through to that channel's output.Do you have any idea on how I can find these transistors on my receiver?
@ mzacharias you jump to conclusions too fast on your section 4, the dc component at the output may go positive or negative, and not necessarily an leaky component etc ...
I've seen protections systems going bad, and the amplifier never had any problems
@vef445 you have procedures check number 3 and 4 ( pages 14 and 15 ) of the service manual
Do the checks in order and report back
@ mzacharias you jump to conclusions too fast on your section 4, the dc component at the output may go positive or negative, and not necessarily an leaky component etc ...
I've seen protections systems going bad, and the amplifier never had any problems
@vef445 you have procedures check number 3 and 4 ( pages 14 and 15 ) of the service manual
Do the checks in order and report back
I should have been more clear.
In my experience - over twenty years with this type of muting circuits, and 40 years of audio service overall, the "un-muting" voltage to the base or gate would usually be negative, so that the transistor, which is placed across the signal line, is shut off HARD.
In fact, special transistors are used because the reverse bias to the base is larger than most signal transistors can handle.
It is this reverse bias, leaking from base to collector when the transistor is supposed to be OFF, that leaks through.
For this reason, most DC offsets CAUSED BY MUTING TRANSISTORS are negative in polarity.
I see a number of muting transistors on page 29 of the PDF. They are arranged thusly.
So, all tests are positive, protections work as they should, which I'm not surprised about since I can clearly hear and see (voltmeter) the voltage pic before the receiver shut off.
I guess I have to find the transistors pointed earlier in this post as being muting transistors and test them one by one?
In this case, I feel the test would be to identify the malfunctioning channel - and just replace the appropriate transistors on that channel as shown in the service data. Given the high likelihood this is your problem, I feel it would be appropriate just to replace them. There are two for each channel.
They are surface mount devices, and a major dis-assembly will no doubt be required.
Thanks for the reply:) I'm not so concerned by disassemble the receiver, I already did most of it when I re-soldered the output board.
Can you confirm we are talking here about the transistors marked Q410X and Q411X on the attached diagram?
And if I'm looking at the right component, I can see that they are using a RTAN430C which I can't find online but it's indicated a replacement part RN1441. Would the following be of a good fit? https://www.mouser.dk/ProductDetail/Toshiba/RN1441ATE85LF?qs=%2fha2pyFadugsbhVQaX8L8rYXi2U42oWKQNSDaZI%2fYbk%3d