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Cayin A50t biasing problem

I recently purchased this amp on a'gon and having trouble getting it bias. When try to measure the bias I get no reading on any of the pots. When I try to raise the bias, the travel of the pot is very small like 3/4 of a turn. Is this normal. I have had many tube amps so I think I understand the process. I can't believe I have 4 bad pots nor 4 bad tubes. What give anyone?
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Showing 5 responses by larryrx7

larryrx7's avatar
larryrx7 OP
137 posts
 
I want to thank you guys for the tips..It actually was the probe length. I went to radio shack and bought a pair with longer probes and it worked. That was really wierd. I have had alot of tube amps and that was the first with that issue....Again thanks
larryrx7's avatar
larryrx7 OP
137 posts
 
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?
larryrx7's avatar
larryrx7 OP
137 posts
 
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.
larryrx7's avatar
larryrx7 OP
137 posts
 
I have 2 meters so I don't think its the meter. There isn't a switch to select the pots so I can't figure this out
larryrx7's avatar
larryrx7 OP
137 posts
 
Yes but I am measuring voltage instead of current in this amp.
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