EH Scott Radio Enthusiasts

The Fine Things are Always Hand Made

Comment by David C. Poland on March 15, 2020 at 6:29pm

Very Nice AC-10 amp !

The tall metal cylinder to the right of the 80 rectifier is a substitute for an 2 pin large smoked glass globe Amperite Self Adjusting Line Voltage Control tube. The primary of the power transformer is designed for 80 Volts AC, per a Scott diagram I have . The Amperite tube acts as a variable resister. From an Amperite tube box I have: "Automatically Controls Line Voltage Line Fluctuations Between 95 and 130 volts"

The Amperite tube replaces the hi-lo switch of earlier production  AC-10 amps.

To protect your power transformer, and as a way to assess incoming line voltage with that Amperite substitute  you have,  when first powering your amp after electrical restoration, monitor the ac voltage presented to the transformer primary (after the substitute) for a reasonable AC voltage and at the same time monitor the B+ voltage is near either:

1) 140 volts DC at the high end of the big ceramic voltage divider. or

2) 135 volts B+ terminal to the receiver

(FYI - I have your version of the late version AC-10 amp (unrestored.) in my collection)

-Dave

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