R/E/P Community

R/E/P => Klaus Heyne's Mic Lab => Topic started by: MikeCheck on April 26, 2017, 01:58:56 AM

Title: M49 Decoupling Cap (C5) Replacement
Post by: MikeCheck on April 26, 2017, 01:58:56 AM

Hello!
So I have an M49 with a failed decoupling cap (C5). Anyone have any experience with replacing this cap and picking a suitable substitute?

Thanks!

Title: Re: M49 Decoupling Cap (C5) Replacement
Post by: klaus on April 26, 2017, 12:41:00 PM

First,  I would like positive confirmation that this capacitor actually failed. In 30 years of dealing with them, both in M49 and U47/48 I have never had a single one fail.

But, if indeed the cap is shorted (?) your choice will audibly affect the sound of the mic: some swear by wet tantalums, others by oil-soaked contraptions. A very good film and foil (not metalized poly-prop!) will add a bit more clarity without thinning out the sound, while those film & foils made with other metal films typically sound more pointy in the mids and highs.

Contact me privately if you want to replace with original material-these days collectors collect everything...

Title: Re: M49 Decoupling Cap (C5) Replacement
Post by: MikeCheck on April 26, 2017, 02:33:00 PM

Thanks Klaus,

I'm very positive. I was loosing my plate voltage after the 200K plate resistor. I swapped the cap out with 1.0uf MusiCap and everything was back to normal.
Honestly It was the last thing I expected myself. I'll triple check just to be sure, but I'm 100% at this point.

Title: Re: M49 Decoupling Cap (C5) Replacement
Post by: klaus on April 26, 2017, 04:03:04 PM

Before signing off on your diagnosis, I would remove the capacitor from the mic and put it on a capacitance tester.
KH