Strange noise when powering up AVR

[madan1]

Hello everyone.

I had this topic posted in the Audio section, but nobody replied there.
Since this is not that much audio-specific, in this section there could be people who might help.

Here is the original post:

...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.
..
Find attached wav file with the noise 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?

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

this is the wav attachment
https://www.badcaps.net/forum/attach...4&d=1492791503

[Andrew F. Ali]

Re: Strange noise when powering up AVR

High frequency sound developed in the transformer??...If the system is working even with this new sound then we may not be able to 'fix' it as all voltages etc would be correct for start-up and play. When it stops working as it should then and only then might we be able to help......My advice...Don't worry about it until it stops working.

[madan1]

Re: Strange noise when powering up AVR

So you are saying it is the transformer?
What is the cause behind that new "feature"?

The voltages seem to be fine.. at least according to the inbuilt system/service menu.

[R_J]

Re: Strange noise when powering up AVR

The "sub transformer" is the switching supply for the +5.5 volts, it supplies the voltage for the relay coil, I suspect when the unit is turned on the relay coil current is enough to make the power supply make a noise, I would suspect c2021,24,26,27,35 or maybe the ones in the primary like c2010 or c2017

[petehall347]

Re: Strange noise when powering up AVR

does it have a slow start resistor ?

[madan1]

Re: Strange noise when powering up AVR

..When it stops working as it should then and only then might we be able to help......My advice...Don't worry about it until it stops working.

and here we are again
It got worse - it started to make more noise after that initial "start-up" sound. For now that "after noise" disappears after some time ( <1min ), but it looks like it affects some of the functionality.
In the service menu all V are within the specs, but I noticed some errors in the communication between the modules on the hdmi board ( cpu <-> dsp1 ). During the time when the noise occurs the unit refuses to play network and tuner streams ( still multi-channel input which does not go through the hdmi board plays fine, which means that at least the power amp section is not affected ).
So anyone willing to reveal what causes that psu(?) noise... choke? transformer? caps? ....???
What could be the cause to develop that problem?
I suspect that I have a bad pc psu ( pc working fine but the psu is making high-pitch sound ) and the pc is my main audio/video analog/hdmi source ).. could be it?
I also have placed the yamaha on my subwoofer ( it had to be temporary, but... )... so could be the vibrations? .... or is it just bad luck?
All the equipment uses the same wall socket ( common ground ).

[madan1]

Re: Strange noise when powering up AVR

Aaaaand it died... all "smart" functionality ( usb, network, radio, etc. ) got broken. Basically I was left with not that good* sounding power amplifier ( multi channel in ).
So, long story short - after resoldering the main power pcb ( the one with the standby/low V transformer ) now everything seems to be working fine.
I guess the vibrations from the subwoofer were the root cause... then cracked solder joints, ripples and so on.
Now I'm sorry that I forgot to hook that board to the scope to see whats going on there... I only tested the other power board ( powered by the main transformer and outputting +/-7 and +/-12V ).


*personal opinion