[R-390] HP521 / R725/audio chassis

[mdmerz]

Hello, I’m wanting an HP 521a or c counter and am thinking maybe there’s somebody here that has one to trade, or knows of one, for some R390a components. I have modified 390 i.f.  sub-chassis that makes R390a into R725 and also have modified R390a audio sub chassis modified with push-pull 6360 output tubes according to Kleronomos. These are modified chassis that are interchangeable with original sub-chassis with no changes to the main chassis of an R390a. These sub-chassis units are currently installed in a working R390a and were modified according to published directions by me for substitution into my receiver, so their circuitry is documented in Electric Radio and they provide some benefit to performance. 

Dan

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