The AA8V 6x2C Crystal Controlled Converter
by Greg Latta, AA8V

B+ Power Supply Circuit Schematic Diagram and Circuit Description

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Schematic Diagram and Circuit Descriptions Page

Introduction:
The 6x2C converter draws very little B+ current. As a result, the B+ power supply uses a simple half wave rectifier. The output is smoothed by a pi filter consisting of three filter capacitors and a resistor. The tube filaments are powered by a 6.3V AC winding on the transformer.

B+ Power Supply Circuit
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B+ Power Supply Circuit:

Power Transformer Secondaries: The power transformer is Heathkit transformer salvaged from a gutted Heathkit VTVM. The high voltage secondary is rated at 125V at 15mA. The filament secondary is rated at 6.3V AC at 0.75A.

Rectifier Diode: A simple half wave rectifier is used in the 6x2C converter. Just about any diode with a PIV rating of 400V or greater can be used here. A 1N4004, 1N4005, 1N4006, or 1N4007 would be fine here. I used a 1N4007 because I had many of them on hand. .

Pi Section Filter: The output from the rectifier diode is direct current (DC) but with a large alternating current (AC) component superimposed. A pi section filter removes the AC component providing clean DC. Input capacitor C3 does an initial job of smoothing out the pulsations from the rectifier. The current then "leaks through" resistor R7 to the output capacitor consisting of capacitors C4 and C5 in parallel. These remove any remaining pulsations and provide smooth DC to the converter B+ circuits. The capacitors are rated at 200V. I used two 47uf units (C4 and C5) in parallel for a total of 94uf because I had them on hand. A single 100uf unit in place of C4 and C5 would work here just as well..

Tube Filaments: 6.3V tubes are used in the 6x2C converter. The filaments draw a total of 0.75A. A single 6.3V winding on the transformer supplies the required current.

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If you have any questions or comments, you can send E-Mail to Dr. Greg Latta at glatta@frostburg.edu