Audio Research D70 mark1 + schematic

I believe that unit shares a similar power supply with the D115 in which case there are indeed solid state devices in the voltage buffer circuit unless somebody removed them. It's important that they be functioning properly or the output of the amp will be noisy. It consists of 2 bipolar transistors, D40k1, a TIP device, and a TLO71 IC. When I get to my office I can give you the proper working voltages. There should be (3)6922 inputs followed by (4) 6FQ7/6CG7 drivers and then the output 6550's. In the regulators there is (1)12AX7 and (1)6550.

Thanks for Your answers ! Yes , Hifigeek 1 ! All components You describe is the same in this amp . I´d be very happy if you could give me the voltages you mentioned. Stewen

The voltage on the collector of TIP41 is 335Vdc. On the emitter of the TIP41 it's 327Vdc. They may vary a bit but the 8Vdc difference voltage should be the same. If it isn't, the buffer has issues. If you are unfamiliar with measuring high voltages, do not attempt this. Sometimes the probes can load the buffer down. It is not necessary to have the output tubes in the amp when you measure the buffer voltages, but you will need a variac to drop the line voltage to 115Vac if you remove the output tubes as a load will not be on the main filter cap bank and they may see an over voltage.

Thanks for Your interesting and valuable answer ! I am used
to measure high voltages as daily working with guitaramps .
Another thing that puzzles me : both schematics I have show
R31 and R32 ( anoderesistors for the last 6FQ7 tube ), 62kohms. The amp I have here , has 33 kohms and it really seems that they are factorymounted !!!! They are 5Watt each.
Wouldn´t that give a higher anodevoltage ? and also a bit higher anodecurrent ? But perhaps lower swing ??
Thanks for some comments. Stewen

V6-7 plates should have 240Vdc on them. Measure across each resistor to make sure they are 64Kohms. Do they say 64Kohms on them? I believe they were black Dale wirewound resistors. They should be the same on both channels. Hopefully someone didn't replace that A.C balance trim pot and change it's value which should be 10Kohms.