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Notice the nonstandard bias
transformer and bias control variable resistor in the bottom
view right. This was later replace with a standard Collins
bias transformer and standard bias pot during the restoration
process. Typically these amplifiers have been tinkered with
in the bias supply area. The old style diodes have been
replaced and the old style electrolytics have been updated.
Another update area is the replacement of the 12AL5 in the
ALC circuit with a diode. This diode modification is factory
derived and later serial numbers deleted the 12AL5 replacing
it with a diode.
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