Strange noise when powering up

[madan1]

Hi there.
Recently got a second hand Yamaha RX-A1010 receiver. It was working just fine for some time, but then suddenly developed a new "feature". When powered-up from long stand-by it makes a "camera-flash-charging" noise.
I still have not opened the hood ( there is a warranty label which I prefer to keep in case decide to sell it ).
Find attached a wav file with the sound and the service manual.

From the schematics of the power supply ( pg 133 ) , it looks like the noise is happening when the main power relay RY201 closes and powers up the transformer. From there ( pg 132 ) there is another relay ( ry109 ), a rectifier bridge ( d1050 ) and the big 12000uF filter capacitors ( c1105 c1106 ).
So I guess the noise is associated to the charging of the caps? Is it the transformer or the caps?
For now I do not see/hear any issues with the functionality of the receiver, but is it possible to get worse?

By the way, what's the point of the RY109? Is it selecting different voltages for the amp side... something like "eco" mode?


p.s. the manual is too big so had to upload it here -

[madan1]

Re: Strange noise when powering up

And here is the development - after some time it started to make noise even after the boot procedure. At first the noise was stopping after some time and after that all features worked fine. Then the noise started to be continuous and some of the "smart" features stopped working.
At that time I finally opened it and after several temporary fixes ( resoldering the power board ... which at this moment I cannot explain why it even worked ) I think I finally was able to find and replace the problematic parts.
With tapping different components I was able to find the problematic nodes - two pulse power supplies - ic943 and ic944 ( BD9329AEFJ ) on the hdmi board.
So, I resoldered the pins of the chips, replaced the two big smd inductors and for a week the unit has been working fine.
I also have some scope screenshots from the time when the noise was occurring and I can upload them here if anyone is interested.
Now I'm just uploading some visual aid from before and after.


The strangest thing was that the unit was booting up fine, no errors were recorded and the system menu was showing all Vs withing the limits.

[jiroy]

Re: Strange noise when powering up

Thanks for sharing ..