I just recently installed the SDS Capacitor replacement board on my two Dynaco MKIIIs.
These amps were bone stock, factory assembled units.
After installing the SDS boards, I fired them up, and attempted to bias.
What I found was that I could not get the bias voltage (measured at the stock test point) down to 1.56, about 2.4 is the lowest I could get it.
So I started checking voltages. What I found is that I'm only getting 372 volts DC at pin 8 of the Rectifier tube. The PT is putting 425 Volts AC onto pins 4/6 of the rectifier. Even if I disconnect the wire going from pin 8 of the Recto to the SDS cap board, I still only get about 390 VDC.
Bad rectifier, you say? I have 4 GZ34 rectos and all give me the same reading.
I must be missing something simple, because, like a moron, I did the mod to TWO amps at the same time, not firing one up and leaving the other for reference. Both amps behave exactly the same, so I 'm thinking I missed something simple...
Before me messing with them, they both worked fine, biased to 1.56 V, The Recto was out-putting around 500 Volts(seeing that is what scared me into replaceing the Cap can.) Everything was cool. Let me see if I can upload some pics of the boards inatalled into the chassis.
Thanks for any help.