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Author Topic: Old Crest 7001 repair question for old techs.... MBS4991???  (Read 1314 times)

yeomanservice@verizon.net

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Old Crest 7001 repair question for old techs.... MBS4991???
« on: March 07, 2018, 03:01:18 pm »

Hello,
Anyone out there have experience with repairing very early Hawthorne NJ Crest Pro Series amps?
There is a pair of MBS4991 (Silicon bidirectional switch) at the front end of the output board. 
The purpose as far as I can tell is as a voltage clamp at the first transistor stage.  Never noticed them on other Crest amps and
they don't show up on any of the schematics that I have. Which leads me to believe that it was a bad idea to have
them there in the first place. Which leads me to think that leaving them out might be a good idea.  Anybody care to weigh in?
Thanks!
John       
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John Roberts {JR}

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Re: Old Crest 7001 repair question for old techs.... MBS4991???
« Reply #1 on: March 07, 2018, 05:19:02 pm »

Try asking Peavey service.

I think JD Bennet might still be around (working in analog engineering group).

Ask service to ask JD...

JR 
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Listen to what a properly "cleared" drum sounds like.   http://circularscience.com/
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