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Subject: [Amps] SB-220 PROBLEM (FINAL)
Date: Tue, 16 Sep 2008 18:35:32 EDT
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Latest diagnostic info........Disconnected one leg of the secondary AC side  
of the transformer going to center junction of the 8 caps in the doubler.   
Tried it again, and the plate meter still moved and the grid meter went  
negative, however it took more ac mains voltage to produce a significant  
movement on 
the meter.  Next I disconnected the other AC lead going to the  diodes so 
that the secondary of the transformer was totally out of the 
meter does not move at all with full main voltage.   Looks like there is 
leakage on the power transformer to ground, I took a  measurement across the 
meter as it was moving and its only millivolts, but  enough to cause the 
problem.  Suffice to say the power transformer is  leaking. Guess we'll need 
another transformer.  This amp is one of the  first made so the thing is pretty 
old.  Time to lay to rest.   Lou

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