JMP 50 Plate voltages mismatch

guitarist1977 · Post by **guitarist1977** » Wed Sep 02, 2015 6:02 pm

HI Everybody.

I see an issue that is bugging me for quite a while.

When my volume is set to 0 or up to about 9 all voltages are correct. When I put volume to 10 the voltage on the plate of one power tube is lower then on the other.
V4 pin 3 - 414V
V5 pin 3 - 439V.

Tubes are biased correctly and bias current is within the limits although some small difference is there.
V4 - 39ma
V5 - 34ma.

I double checked it with different tubes - behavior is the same.

And it is only on the socket closest to preamp sockets.

Also I changed tube sockets and it did not helped.

Did anybody have similar issue?

Thanks,
Alex