Help! Yamaha RX-V481 relay click sound repeating.

Hi All:
My Yamaha RX-V481 suffer the relay click sounds repeating issue.

After open the case and comparing the service manual, the output stage relay is suspected.
But after I change the relay(RY221/RY223), the click sound repeating can't eliminate.
Have any one suffer the same failure problem?

B/R
rx-v481 ckt.jpg
 
Generally, either a fault/failure in the protection circuit or excessive
dc voltage is finding its way to the speaker outputs. As a starting point suggest
measure the dc voltage at either pin marked in blue, black probe connected to any
black speaker post/connector or chassis. Repeat for either pin marked in green and
chassis. Expect less than 100mV (ideally 0mV), check for any voltage spikes.

1656753525944.png
 
Hi Guys. Tks your comment. I have follow your instruction to measure the blue an green part.
It shows mV.

rx-v481 meas.jpg


I also check the others, there is something wrong.
rx-v481 npn.jpg

I found the PRY/DEST DC level is lower than normal. Maybe the Q5401(20V_NPN) may be the root cause.

B/R
 
Guys! tks your comment.
The Q5401 bias voltage is DC value. But the B-E voltage drop is about 1.5V. I think it is not correct.

For Q2179/Q2180, it is hard to measure, so I measure the CB223/CB522. Each point DC voltage is correct and stable.
B/R
rx-v481 meas_2.jpg
 
Possible solution
I have a Yamaha RX-V383 which suddenly developed exactly the same symptoms shown in the OP's video. As soon as the main relays clicked on after starting up they would start to cycle on and off and the unit produced no sound.
Resetting to factory defaults in the advanced setup menu didn't change this. Entering the service menu (power off, keep Tone Control and Info pressed then press Power) yielded a NO PROTECT message indicating that none of the protection mechanisms had been tripped.
I opened the top and couldn't see any sign of component damage (swelling, leakage, scorch marks, etc).

I googled hoping to find a quick fix and my heart sank when I found this thread.

But ...
Before giving up I tried inserting some headphones. This caused the relay cycling to stop and sound came through the headphones. I inserted the headphone jack a couple of times and noticed that the cycling began taking a few seconds longer to start on powering up. So I tried just wiggling the headphone jack around in the socket. After doing this a few times (insert jack, wiggle slightly, pull it out a bit, wiggle some more) the relay cycling suddenly stopped completely. Since doing this I've had the unit running and producing sound for over ten hours in total with no recurrence of the fault, leading me to think it's fixed.

I suspect that some dirt had worked its way into the headphone detect switch in the socket and was managing to toggle it causing the speaker output relays to cycle on and off. So if you have this problem it might be worth giving the headphone socket a clean (some compressed air might be the best way) before performing major surgery.
 
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