Cayin A50t biasing problem

Are you sure that your probes are touching the bottom of the bias test insertion points? On my amp the insertion points are quite close together. The probes get in way of each other and didn't reach to the bottom until I cut away some of the plastic that was sticking out from the side of the probes. Until I did that, I could not get a reading.

I have the same amp and totally agree with Ttbolad. Conventional probes don't get to the proper contact points-and if they do, only for a brief instance, with not enough time to give the correct reading. This may be what you are experiencing. I haven't gotten a new, longer, set of probes (yet) but solved my problem by wrapping a paperclip around the probe, and crimping tightly (I'm sure decent wire would work--to extend the probe). Not the prettiest, or best solution, but it worked. My bias is dead on.

Here is another suggestion - since I just blew a fuse in my VP-100i. DON'T stick the common (ground) probe in the well on the same side of the amp as the hot probe. Use the common on the opposite side of the amp. That way you won't have to trim the probe. Also you will avoid a short. If you touch, or get real close for that matter, to the common with the hot, the probes can arc and blow a fuse. I just did that. How stupid of me to not see that the probe wells were designed so that it would be difficult if not impossible to get a reading with both probes on the same side of the amp. If you use the common on the opposite side, all is well - and you won't blow a fuse.

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