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In Reply to: RE: Music Reference RM-9 posted by DAK on March 19, 2014 at 12:54:01
In one of the amps I was taking care of I had to replace the bias trim pots. They were thermally damaged after so long in service.
I've attached the only RM-9 schematic I've ever seen. It's not a particularly clear picture. I assume it is a few generations removed from the original, but don't now remember where I even got it. I've never seen a Mk II schematic, but from the looks of the one I serviced the differences are minimal.
Kevin Carter
K&K Audio
www.kandkaudio.com
Follow Ups:
Thanx a million Kevin. I noticed that there are 3 zeners per channel. Unfortunately, I can not make out the values of those zener diodes. Is it possible for you to tell me that. best regards, Dak
I'm afraid I have no memory of the zener diode part numbers or voltage values (if I ever knew them), but it's easy to place a voltage across the zeners with a current limiting resistor to measure what they are. I would be careful about blaming the zener diodes for your problem until you've assessed the other components that comprise the bias network. Zeners are typically very rugged unless asked to pass way too much current.
Kevin Carter
K&K Audio
www.kandkaudio.com
Thank you for the tips. I will go in there and take a better look at things. I know the bias circuit was problematic when I bought the amp maybe 10 years ago. Since the previous owner gave me the replaced parts which was a cap and a pot. The amp worked ok but was not the sound I wanted so I sold it to a buddy. Now several years later the bias is giving problems again. regards, dak
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