Neuman Pre-Amp problems

Hey all! Been some time since I've been on the board, other projects keeping me busy these days.

I am helping out a friend fix up an old Neuman Mic pre removed from a board. The Model is:

TYP. PMV 70 930 U1

Does anyone have a schematic or working knowledge of this unit?

The resitor R39 whic I believe is 47 ohms keeps burning up.
Also it goes to the +V of the Op Amp.
The voltage across the resistor is 22VDC.

I really could use a schematic!!

Or any help is great too!!


-ChuckD

Hey Thanks !!!

Ooooooo R39 is in fact a current limiter on the op amp. For that guy to burn up the Op-amp might be shorted. I must go home and check that. That would be bad news.

I wonder if Fred Forsell makes a good replacement Op-Amp to fit in there.

-ChuckD

damn I was right!

The op amps are blown. They are OA12s ...

I put in a LM833 instead and the unit works again.

Does anyone have a replacement or better??? The footprint is not a normal one. Kind of verticle un like most of the flat square ones I've seen.

Ideas??

-ChuckD

They are OA12s ...

I put in a LM833 instead and the unit works again.

Does anyone have a replacement or better???

Click to expand...

Are these the Op-amp made by Neumann? Then you could try to ask here:

http://www.audiosonic.de/set-neumann.htm

Click to expand...

They are the official Neumann-Mixer-Servicestation in Germany.

Chris

I don't see my exact unit but here are the op amps !!
http://www.audiosonic.de/pdf/V457-2B.pdf

Yes they look like they were a Neuman build.

I am looking for anything really that would fit the same as these.
Or I will try to contact these guys too.

Thanks!

-ChuckD

I have OA12s and OA20s and replacement boards with NE5532 we use at work.

PM me if you are interested.

Hey thanks Volker!

I just PM'd you


-ChuckD

I have a sick one of these and am unable to find the problem. It works in the lowest three gain positions and beyond that it's dead.

Any ideas?