68kMLA Classic Interface

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PB3400c - coil whine?
Posted by: ObeyDaleks on 2025-09-23 11:05:29
Getting some annoying coil whine from a freshly recapped 3400c. I believe it's coming from a 10µH inductor on the main board under the DC power board. I'm thinking this is a known design flaw? Is that the reason for the weird foam insulator around it? Can anybody confirm?

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Posted by: MacUp72 on 2025-09-24 00:35:39
have you checked if the powerboard is ok, eg replaced/compared it with a known working one?
IMG_0858.jpeg
Posted by: ObeyDaleks on 2025-09-24 21:53:15
I don’t have a spare DC board, unfortunately. The machine works fine but then again coil whine generally doesn’t indicate any underlying problem.

I was just curious if anybody had the same experience. The insulator around the inductor is pretty suspect. Honestly, I probably wouldn’t notice the noise if the machine still had its original spinning disk.

I might just silicone all the inductors and see if it improves.
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