Cayin A50t biasing problem

I own a A55T. When I bought it i was told to use sharp ( pointed) electrodes to do the measuring. If it has a blunt tip it won't measure anything. Maybe this helps. Good luck.

To answer Williamredburry idea...I do have a very small reading of about 15-20 MW so I think I have a circuit connection...Newbee, you might have something but since I have a low reading, I think it may be a faulty bias circuit but it is kind of odd it would be in all the pots. I had one once that had 1 bad one. What do you think?

Larry, are you saying that you have a 15 to 20ma reading regardless of the rotation of the bias pot(s)? Or that is the maximum reading available? Is there any difference in the reading between the 4 tubes/locations? You know it is entirely possible that your have some seriously exhausted tubes. Do you know their history? Do you have any spares - you could always sub in a good one and see what happens.

Hi Newbee....I rotated in three different quads including a new quad of SED winged c's and what I am getting is a maximum of about 20ma. Being in all four pots is puzzling.

Larry, There is something in the bias circuitry that is common to all four pots. The meter! I'm not thinking it is broken, though it might be. What I'm thinking is that something between it and the pots is defective, for example the switch where you select the pot you want to adjust or, more likely, the connections between the switch and the meter. Just a guess. Maybe you need a techie to take a look.