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R/E/P => Klaus Heyne's Mic Lab => Topic started by: terskelton on March 15, 2021, 09:09:24 PM

Title: NKMu Neumann PSUs
Post by: terskelton on March 15, 2021, 09:09:24 PM

Hi. I have three different types of Neumann NKMu power supplies for KM56 mics and none of them match the one NKM schematic I've found.

One version has the Stabilyt cells and a tube, one has a completely different pc board with a big power transistor mounted on it, no tube and no Stabilyt cells and the third version has a different board with small "plastic" board underneath with what may be a wirewound resistor with a couple of taps to maybe adjust the heater voltage.

Up top is a small pc board with three caps, some resistors and maybe a Zenier diode mounted to the transformer with a metal strap. I'm in search of schematics for these and any thoughts anyone has.

Needless to say the three units with Stabilyt cells are all corroded and the cells and plastic mounts are broken.
Thanks.

Title: Re: NKMu Neumann PSUs
Post by: klaus on March 16, 2021, 12:42:35 PM

You have a serial number for the unit?

Title: Re: NKMu Neumann PSUs
Post by: terskelton on March 16, 2021, 04:41:14 PM

One of several with the tube and Stabilyt (assumed) cells is 1073; one with no tube/Stabilyt and small PC board on top with caps and maybe Zenier is 1613; and the one with a power transistor on the main board with B+ pot is 10634 (no tube/Stabilyt). Thanks Klaus.

Title: Re: NKMu Neumann PSUs
Post by: klaus on March 16, 2021, 08:10:03 PM

I know of two versions: the original, with Stabilyt, the other with the transistor/Zener replacement for the leaky Stabilyts in the heater section. Could the third be a home-made modification?

Title: Re: NKMu Neumann PSUs
Post by: terskelton on March 17, 2021, 01:41:07 PM

Klaus, Here are photos of the two mystery versions. Hopefully you can still se adequate detail after compression. Thanks.

Title: Re: NKMu Neumann PSUs
Post by: klaus on March 19, 2021, 12:41:27 PM

Here is what I have in additional schematics pertaining to NKM supplies. Any of which may help you authenticate whether the circuitry in your units is original, an official add-on or third-party:

* NKMu 00-00-02 5 from 1-62, starting with Ser.# 901
* SK 73t 930-01 from 7-64
* SK 33d from 8-68

Best of luck1

Title: Re: NKMu Neumann PSUs
Post by: terskelton on March 27, 2021, 01:27:07 PM

Hi Klaus, Thanks but I don't see the actual schematics??

Title: Re: NKMu Neumann PSUs
Post by: klaus on March 27, 2021, 01:49:24 PM

Message sent 3-22-21