I mistakenly deleted the message from the fellow about the Centurion
problem so I'm sending this to the list.
I appears that the bias cutoff circuit has failed and is not cutting off
the amp in the standby mode. The components for this circuit reside on
the 81537 Filament-AC board and consist of:
D1 1N5344 8.2 V Zener
Q1 2N3055
Q2 MPSU01
a 30 V MOV
That's what in my Centurion which is serial no 40A10072 (April 1992).
Most likely the Zener and/or the MPSU01 transistor have failed.
The purpose of the circuit is to apply a slight bias to the tube to cut
if off in the standby mode. If the tubes are not cut off they will draw
100 ma or more or current. At 100 ma and 2500 volts, that's 250 watts
being dissapated with nothing going on! That will warm up the cabinet
quite nicely!
73,
Puck, W4PM
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