• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Audio Research D76A bias adjustment

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Raiser

Member
Joined 2004
Dear All,

I'm having problems to adjust bias in an Audio Research D76 A. In one 6550 I found about 50mA and it is possible to adjust it. In the other tube there are more than 70mA and it is not possible to bring down this value.
This problem happens in both channels.
I've already changed the 1N4005 as well as 1N5368B and both 50uF x 150VDC in the power supply responsibles for this negative voltage. It remains the same problem.

Thank you for any advice in solving this problem.

Regards
Pedro
 
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