[TenTec] Centurion Problem

[H. M. 'Puck' Motley W4PM]

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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