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[studerfreak]

In my KMS85 microphone I saw a capacitor which seems to be a tantalum capacitor.
No print of the value/voltage, but just a "pearl" with a red top, yellow bottom side and a black dot on one side.
I figured it may be a 20uF capacitor, but what working voltage ?
And what would be a good replacement, if this value is not available anymore.

[klaus]

Have you by any chance posted on the Neumann site about wanting to replace tantalums in your KMS 85?
I was tempted to respond: they rarely if ever fail, as shitty as they may sound in the audio path. But that would have been another topic than the one you started there.

So, which tantalum did you want to replace, and why? Because that will determine the need and component value. I would in any case, not substitute with another tantalum, not even the ones that are filter caps, but would look for a good polarized electrolytic, like a good quality Panasonic or Elna. The voltage rating for all applications should be 63V. (Larger ratings may not fit).

[Dick Swaneveld]

Hello Klaus,
Yes, I posted on the Neumann forum for getting the schematics.
And I received that from Uwe already.
Reason for asking about the tantalum capacitors is that I found a 1uF/50V one which was leaky (tested with a real ESR70 capacitor tester).
I think it was C10 (or C9).
Replacing that with a new one got the KMS85 back to life again.
Is it a good idea to replace the tantalums with Panasonic or Elna's now I am at the inside of the mic ?
Thank you !

[klaus]

Yes, especially since you found ONE bad one already.
They were all made around the same time, and most likely by the same manufacturer, so it could conceivable be not the only one in the batch that was bad (though the others used in your mic are probably all of higher value).
Especially the source bypass capacitor should be looked at.
Edit: I just received the schematic from Uwe Sattler, former Technical Director of Neumann, and I see that this a variation of the U47fet and U89 op-amp.  No source cap present.

[Dick Swaneveld]

The KMS85 I have has 4x 1uF/50v, 1x 2,2uF/35v, 1x 4,7uF/6,3v and 1x 0,33uF/50v, so there are two with a higher value.
The source bypass cap: Is that the 2,2uF/35v ?
Which Panasonic / Elna types would you suggest ?
Thank you !

[klaus]

Try the Elna Silmic II.
And, sorry, I erroneously referred you to a U87 schematic. Please see my correction further up.

[Dick Swaneveld]

Schematic I have got and pc board of KMS85 say "930-02"(label on transformer).
Do you mean the 1uF/50v cap between R6-R13 (1Megohm) to ground ?
I have found that the output signal of the KMS is quite low.
And that this is correct, looking at the specifications of the KMS85 and other KM types.
Is that done for obvious reasons, like the fact that this mic was supposed to be handheld and used at a short distance ?
Is it possible to raise the output level ? The transformer is already factory set for 200 ohms.

[klaus]

See my corrected post above.

[Dick Swaneveld]

Thank you, Klaus !
Looking through the Elna Silmic II range I saw that for the existing 20u/3V (C7) and 0,33u/50V (C3) they do not have a replacement type.
What would you suggest as a replacement value/voltage ?

[Jim Williams]

.33 at 50 is a small value. I would use a metalized mylar cap, it should fit. Then no more worries about that part.

22uf at 16 or 25V Panasonic FR series would be a great replacement for the other cap.

[Dick Swaneveld]

Thank you, Jim !
Do you know how to get a bit more output level from the KMS85 ?