One of my 12FM6 tubes won't behave - the bias is not consistent from day to day.
Yesterday, after having my Millett on for about an hour, I checked the bias and found the tube bias for this particular tube at 15.75V. I adjusted the trim pot and brought the bias down to about 15.10V. Today, after having the amp on for about an hour and listening to a movie through it from my laptop, the tube is reading 14.64V!
The other 12FM6 tube in my system is fairly consistent and ranges around 15V - 15.25V after a 30-60min warm up.
Both tubes were matched by Beezar.
The MOSFET biases are pretty consistent and typically are around 230mV after a 30-60min warm up.
Any ideas as to why one of my 12FM6 tubes might be inconsistent? Could it be due to the fake ALPS pot?