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Old 1st Aug 2011, 3:55 am   #9
PEHamel
Retired Dormant Member
 
Join Date: Feb 2010
Location: Long Beach, Mississippi, USA.
Posts: 30
Default Re: circuit diagrams.

First check the tubes.
Look up the diagram of each tube.

Most of the time anode-screen troubleshooting can fix almost any tube amp.
First check voltages on empty sockets. A missing voltage in one channel and not the other has it down to the stage. You really don't need to trace an entire circuit except where you find a voltage missing or way too high.

Get some tube extenders (or spend hours carefully wrapping small wires around one pin at a time of each tube).

Similar channel tubes should have the same anode voltages and screen voltages.
The tubes with wires running to the output transformer are the output tubes and should have the highest voltages.
The grid voltage should never be positive in reference to the cathode.
The input tubes use less voltage than the output tubes.
These general principles can keep something running without needing to recreate the entire diagram.
Good Luck
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