Hello All:
I have a 1973 Fender Bassman 100 (Master Volume) head that is running HOT and the chassis itself is hot!
Prior history:
a) Power tubes were shot.
b) One of the 470 ohm resistors on the power tubes was burned or open (I forget - it's been a while since I looked into this amp)
b) 100 ohm filament resistors burned or cracked in half
c) Had a hum from a bad ground on one of the power tubes.
Current state:
a) New Filter and Bias caps
b) New master volume pot (1M)
c) New 100 ohm filament resistors (original were cooked)
d) Grounds were all re-soldered
e) Replaced all the 470 ohm and 1.5K resistors on the power tubes
e) Amp is running with 446V on the plated and idling at 23ma to 25ma with a matched quad of Sovtek 5881WXT's
The amp is quiet (no hum) and sounds good (no distortion).
I think the tubes are running at a reasonable operating point in terms of idle current - maybe even a little cold (not sure).
Any ideas why it might be running unusually hot?
Could the power transformer be damaged even though the voltages look reasonable?
I have a 1973 Fender Bassman 100 (Master Volume) head that is running HOT and the chassis itself is hot!
Prior history:
a) Power tubes were shot.
b) One of the 470 ohm resistors on the power tubes was burned or open (I forget - it's been a while since I looked into this amp)
b) 100 ohm filament resistors burned or cracked in half
c) Had a hum from a bad ground on one of the power tubes.
Current state:
a) New Filter and Bias caps
b) New master volume pot (1M)
c) New 100 ohm filament resistors (original were cooked)
d) Grounds were all re-soldered
e) Replaced all the 470 ohm and 1.5K resistors on the power tubes
e) Amp is running with 446V on the plated and idling at 23ma to 25ma with a matched quad of Sovtek 5881WXT's
The amp is quiet (no hum) and sounds good (no distortion).
I think the tubes are running at a reasonable operating point in terms of idle current - maybe even a little cold (not sure).
Any ideas why it might be running unusually hot?
Could the power transformer be damaged even though the voltages look reasonable?
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