Thanks for your reply, one thing I forgot to mention is plate voltage. The tester has two ways to test, with plate of @ 90v and @ 180v, The preamp runs at from 115 to 137v on the plate. The drift shows most often at 180v, and to a lesser degree in the preamp and seldom at the 90 volt level. Further thoughts?
Tube problems 6922
Hi: I am finding a problem with many 6dj8/6922 tubes that no one seems able to explain. When testing with a dynamic mutual conductance tester (B&K 747b) I am finding about half of the tube's readings won't fix at a reading but will drift up and down continuously. My meter tests all other tubes types fine and half the 6dj8/6922 test ok. Further the meter has just had new caps and calibration. When using these defective tubes I hear artifacts in the music(drop outs, channel imbalance, static). Please email or answer here if you can explain what is happening within the tube to cause drift.
Thanks
Otis
Thanks
Otis