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RD50 self-biasing - how to tweak?

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Chris Metcalfe (chris_m)
Username: chris_m

Registered: 10-2006
Posted on Tuesday, October 31, 2006 - 06:22 am:   

Anyone out there done any work on bias in the RD50's, which appear to be fixed- or self-biasing?
I measure 28/38 mv across the 6.8 ( actually 7.5)cathode resistors, which is about 4-6 ma per tube - much colder than other models. I'd like to increase static current draw to about 12ma, but the RD bias circuit is quite different to other models. Anyone looked at this?