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Author Topic: Sennheiser 421-N Hum Induction Coil and other issues  (Read 32 times)


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  • Real Full Name: Vincent P Cimo

Hi all. I'm repairing a 421-N that had an odd rattling sound. When I opened up the mic, I found that entropy had worked it's magic and the hum induction coil had come completely unwound and turned into a big ball of chaos. I tried unknotting it for about an hour, thinking I could rewind it around the resonator, but eventually the wire broke. Does anyone know what a viable replacement may be? I've talked to Sennheiser support and they have no specs on the microhenry amount of the coil, but it looks like it's about 28 gauge copper wire.

Also, the wiring on the tuchel connector has snapped off, and the wires coming from the PCB are too short, so I have to replace the whole run (from the bottom PCB to the connector area), but I can't seem to figure out how to get in that PCB area to see where the wires are soldered. Does anyone have any advice there?

Thank you!

See attached photos for more info...


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Re: Sennheiser 421-N Hum Induction Coil and other issues
« Reply #1 on: Today at 12:27:10 PM »

It happens more often...

A friend of mine once had a MD421 with a damaged hum compensation coil.
Since there was no information available, I decided to remove the compensation coil and connect the capsule wires directly to the output connector.

As long as you don't use the microphone near transformers (which is often the case) this shouldn't cause problems.

Maybe not an award winning solution, but the microphone worked again and he had never problems after this 'repair'...
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