Question about a weird power supply hum in a repair last month

Christopher Jenkins · 2026-04-11T09:55:05.099174+00:00

Had a desktop in the shop from a cafe in Dayton that would make this high pitched hum only when the CPU was under load. Replaced the PSU with a Corsair RM750x and it went away, but the old unit tested fine on my load tester. Ever run into a PSU that only acts up under a specific motherboard load?

victor806mo ago

Seen that before. Sounds like a weird harmonic resonance with the board's VRM. Old unit probably couldn't handle that specific switching frequency cleanly.

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bettyh846mo ago

Yeah, that's coil whine from the old PSU's transformer... it gets really bad with certain load patterns. I always keep a cheap motherboard around just to test for that specific noise before I blame the main board. Sometimes a little non-conductive glue on the coils can fix it, but swapping the unit is safer.

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abby_carr575mo ago

Bettyh84 knows her stuff, I just nod and pretend I'm not glueing my own shoelaces together.

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