I built a Ceriatone layout JCM-800 2204 and I can't get the bias voltage close. The best I can get is 12-20mv range with tubes installed.
With no tubes installed I have 499v on pins3 of the tube sockets and -35v on pins 5. On the anode side of the bias ckt. diode, I get -45.8mv. Between the 15k and the 56k I have -36mv. The trim pot varies the voltage from 0 to -25mv. Doesn't look like enough range to me. I've doubled the 220k bias range resistor with minimal effect. It gets me another few mv. Any ideas? Thanks.
With no tubes installed I have 499v on pins3 of the tube sockets and -35v on pins 5. On the anode side of the bias ckt. diode, I get -45.8mv. Between the 15k and the 56k I have -36mv. The trim pot varies the voltage from 0 to -25mv. Doesn't look like enough range to me. I've doubled the 220k bias range resistor with minimal effect. It gets me another few mv. Any ideas? Thanks.
Comment