Viewsonic VG800b power supply noise

[sceva]

This one had a couple of bad caps at C4 and C5, and the component to the left of FL1 had a bad solder joint. I replaced the caps and resoldered the joint and it now works. But when it is connected to power and the monitor is turned off there is a ringing(?) noise that seems to be coming from most likely the area in red, but possibly from the area in yellow. I tried the tube to the ear but could not get any closer than that. Are there any common components that most likely could make a noise? Thanks.

[Dgtech]

Re: Viewsonic VG800b power supply noise

I have found caps and transformers to make a hissing noise or a high pitch ring nose.

[sceva]

Re: Viewsonic VG800b power supply noise

I have found caps and transformers to make a hissing noise or a high pitch ring nose.

I replaced the caps, even the big one, but that did not help. Maybe the transformer?

I just googled around and saw this:
Usually, there are 3 reasons why you're hearing that buzzing sound:
1. Bad filter caps on the input side
2. Bad diodes, leaky capacitors or bad optocouplers
3. Loose parts on the transformer that vibrate because of the transformer's magnetic field.

I will check some more. Thanks.

[Th3_uN1Qu3]

Re: Viewsonic VG800b power supply noise

It's usually the transformer or any filtering coils. Some SMPS Shut Up (tm) gets rid of it. Aka brush some lacquer onto the transformer and coils and it's done.

[jetadm123]

Re: Viewsonic VG800b power supply noise

Try this, using the eraser end of a wooden pencil, stick or any else that's insulated, gently push against the metal frame of the transformer to see if that changes the tone you're hearing.

[sceva]

Re: Viewsonic VG800b power supply noise

Thanks for the tips. I did not try the lacquer yet... I did try pushing around on things and resoldering but it did not change, except it might be a little quieter now. I put it back into the case and am letting it test for awhile. It is not very noticeable inside the case... maybe I should put some insulation around the board to further dampen the sound! :-)