Bardagh
Well-known member
I have a 6505 where the power tubes are running inexplicably hot. To try and figure out what going on I added the adjustable bias with the usual 10k pot and a 6.8k resistor in series. I currently have a quad of nominally matched EH 6L6's in it and with the maximum resistance of over 16k these things are still running hot - ranging from 45mA to 38mA. It doesn't seem to be drifting as it doesn't really change from that at idle, but what could be the prime suspect here? I have some other 6L6 sets on order but none on hand, although it seems kind of nuts to me given how cold the 6505 is with the fixed 15k resistor that the tubes themselves could just run that hot.