Hello, This is probably a dumb question, but... I just replaced the power tubes in my JTM 45 (KT66) and biased it at 36ma plate current using a bias probe, then controlling with the bias test point (1ohm resistor from cathode). The reading at the test point is slightly higher, which seems logical since screen current must be added. The plate voltage is 460V, the screen voltage is 463V. Anyway, with the bias probe still installed, I applied a guitar signal. I was expecting the plate current readings to oscillate above and below the idle point. But it seems to only go above, with 75ma peak. Is that normal? Since the average plate dissipation is what is important for tube safety, are the tubes safe in this case? I also observed how the plate voltage changes with signal, the lowest reading I got was 406V. 0,075A x 406V = 30,45W which is 122% of plate dissipation (or worst if peak current doesn't occur at the same time than highest voltage drop). Last thing I did was to put the bias probe on my Blackface Vibrolux, to see if the behavior of the tubes was similar, and indeed it is. That amp has used the same power tubes with no problem for 2 years, so I suppose it is normal. What am I missing?