R/E/P Community

R/E/P => Klaus Heyne's Mic Lab => Topic started by: Donn on April 22, 2019, 01:24:13 AM

Title: U87 mod to remove daughterboard
Post by: Donn on April 22, 2019, 01:24:13 AM

Hello,

In another post, Klaus made mention of a modification to remove the daughter board of a U87 and do the following modification to versions 03 through 05 (mine is an 04). Can someone recommend to me a U.S based tech (including forum members capable of doing the job). I know Klaus is very busy, and it's apparently not that hard (but not easy enough for me to do myself).

Thanks!

(Klaus' Quote):

So if you want to keep the mic stock, you can keep the coupling cap but you may want to throw out the daughter board of versions #03 though #05 and replace with discrete FET, 47kΩ drain resistor, source cap and resistor (which needs to be biased) and add a 1 gig Ω shut at the FET gate.

All this is fairly easy to do (at least for a mic tech)

Title: Re: U87 mod to remove daughterboard
Post by: mbrebes on April 22, 2019, 05:35:52 PM

I just looked at the two different version schematics.  It looks like something a good tech should be able to do.

Title: Re: U87 mod to remove daughterboard
Post by: Donn on April 22, 2019, 07:46:26 PM

"I just looked at the two different version schematics.  It looks like something a good tech should be able to do."

Yes, that's what Klaus said in the quotation in my original post. I'm hoping for suggestions as to where to send it for the work. Tom Onofrio says he mostly just does Neumann repair to stock, not modifications forward or backwards.

Donn

Title: Re: U87 mod to remove daughterboard
Post by: mbrebes on April 23, 2019, 10:45:04 AM

I could probably do it for you.  I am in the Los Angeles area.

Title: Re: U87 mod to remove daughterboard
Post by: soapfoot on April 23, 2019, 09:36:31 PM

Tom Onofrio is a great Neumann tech, as well.

Title: Re: U87 mod to remove daughterboard
Post by: klaus on April 24, 2019, 01:06:16 AM

Read two posts up.