Neuman U87 just stopped working; capsule looks fine.

Before I go to the lengthy process of sending it in to be fixed I thought I’d check here for some quick ideas on what to look for. I was recording extensively for three hours and then I turned of everything off and took a break. I came back a few hours later, turned everything on and it just wasn’t working anymore. This is a modified U87 by a guy in Nashville  named Korby. So I don’t know if the original schematic would help with trouble shooting. Is there way to check components with a voltmeter just to see if anything is dead, etc? 

I would start to measure the voltage on the drain of the FET.
Usually the voltage at this point is in the order of 10-11 Volts.
If there is no voltage at all, something may have gone wrong in the voltage stabilisation circuit. (FET or transistor.)

A common fault in the u87 is failure of the tantalum cap across the main supply zener. Check with a voltmeter round the fet as Ruud said, if you have no volts look for shorted tantalums.

Have you checked the phantom supply voltage on the channel you are using?
Shure has a good write up on how to do this.
Make sure the voltage is in spec.

Is the cable good?

Have you tried another microphone on that channel?

After that is when I would start looking at the U87.

Gus said:

Have you tried another microphone on that channel?
After that is when I would start looking at the U87.

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I tried a ribbon microphone on the same preamp. the mic worked  just perfectly. It doesn’t appear to be the phantom power.

I plug the Neuman you 87 into another mixer supplies phantom power and the microphone was dead quiet. I’m pretty sure it’s the U87  that’s broken.

abecedarian said:

I tried a ribbon microphone on the same preamp. the mic worked  just perfectly. It doesn’t appear to be the phantom power.

I plug the Neuman you 87 into another mixer supplies phantom power and the microphone was dead quiet. I’m pretty sure it’s the U87  that’s broken.

Click to expand...

Your ribbon mic most likely doesn't need (or want!) phantom.  So the channel's phantom supply still may be the problem.  It is also the easiest thing to check!

I checked it with a different mic pre and it still didn’t work.  Being that it is a modified microphone so sent it in to a very reputable repair shop.  Their service was great.  I’m really unhappy.  The mic was put back to factory spec.; the Korby mod is bye-bye and do I miss it. 

Korby and his half brother are apparently out-of-business.  If you have a modified Korby U87 and it’s broken, be aware of how you proceed. 

I guess I will another mod.  So disappointed.

Just interested to know how the mic is differend now. Obviously there is a big difference?