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I have one old power supply, it was dead but i decided to attempt to fix it. Replacing all bad capacitors made it power on again. Since i didn't had one 2200uf 10v capacitor i used one 2200uf 25v capacitor but i guess this should be fine. but then i noticed that terrible whine. https://www.youtube.com/watch?v=NKsqcYnQ_v4 i'm almost sure that it might be a coil or transformer whining on the second stage of the psu(the stage of the high frequency switching), but is packed in a tiny area it made almost impossible to pinpoint where is this whining part. I'm sure it isn't a fan because even unplugging the fan the whine continue. And i can't get a new atx psu because nowadays ATX psu have a strong 12V rail and older ones have a strong 5V rail(for example one Corsair CX600 is a 600W psu but only has 25A rating on the 5V rail, this 'revived' psu has 60A rating)

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  • \$\begingroup\$ "Replacing all bad capacitors". Capacitors can make that kind of noise. Maybe the new ones you soldered onto make that noise. Also, it sound like a capacitor that sits very tight to the PCB, so either a SMD capacitor or one cylindrical that is very pushed down to the PCB. \$\endgroup\$ Jul 17, 2017 at 18:26
  • \$\begingroup\$ Are there any surface-mount components on the back of the PCB? \$\endgroup\$
    – pipe
    Jul 17, 2017 at 18:31
  • \$\begingroup\$ turned out that adding load to the PSU eliminated the noise. after measuring all voltages i plugged the ATX Power supply and the noise is gone. \$\endgroup\$ Jul 19, 2017 at 23:07

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I do this all the time, bringing back 1970s power supplies back from the dead.

Get yourself about 18in of aquarium tubing. Stick one end in your ear. Wave the other end around the board to find the noise source.

Perhaps clean your ears out first. And perhaps slightly shave off or melt the cut edge of the aquarium tubing, so you don't get 'paper cuts' inside your ear canal.

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  • \$\begingroup\$ +1 You can get an inexpensive stethoscope on Amazon or at the bookstore of a community college that trains nurses. Maybe $10. or $15. You can pull the 'sensor' part off to get an open plastic (insulating) tube. \$\endgroup\$ Jul 17, 2017 at 18:45
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    \$\begingroup\$ Until I brought some .25" tygon tubing from home, I was using straight pieces of heatshrink \$\endgroup\$
    – wbeaty
    Jul 17, 2017 at 23:12

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