The Johnson Viking Ranger
by Greg Latta, AA8V

Low B+ Power Supply Schematic Diagram and Circuit Description

Low B+ Power Supply
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Except for the final amplifier, modulator, and clamper circuits, all of the circuits in the Viking Ranger are powered by the low B+ supply. The final amplifier, modulator, and clamper circuits are powered by the high B+ power supply.

A 6AX5-GT rectifier tube is used in a full wave center tapped configuration with a choke input filter. The choke input filter allows the rectifier tube to handle substantially more current than when used with a capacitor input filter. As used in this circuit the 6AX5-GT can handle a maximum total current of about 150mA. Nominal output of the low B+ supply is 300V.

Low B+ Power Supply
Click On A Section of the Schematic
Below for Information on That Part of the Circuit:

Low B+ Power Supply Filter Capacitor Filter Choke Transformer Filament Secondary Transformer High Voltage Secondary 6AX5-GT Vacuum Tube

Or click on one of the links below:

Low B+ Power Supply
 6AX5-GT Rectifier Tube
 Power Transformer T1 High Voltage Secondary
 Power Transformer T1 Filament Secondary
 Filter Choke
 Filter Capacitor

Low B+ Power Supply:
6AX5-GT Rectifier Tube:
The low B+ supply must provide a substantial amount of current. The 6AX5-GT can handle up to 75mA per plate for a total of 150mA. The tube has an indirectly heated cathode, which means that a separate filament winding not needed, and the 6AX5-GT filament can be powered from the same winding that powers the rest of the 6.3V filaments in the transmitter.

You can click here for a 6AX5-GT data sheet.

6AX5-GT Tube

Power Transformer T1 High Voltage Secondary:
Power transformer T1 powers all of the power supplies in the Ranger. Three pairs of secondary taps for the bias, low B+, and high B+ supplies are provided, along with a secondary center tap.

Transformer High Voltage Secondary

Power Transformer T1 Filament Secondary:
Power transformer T1 also supplies the filament power to all of the tubes in the Ranger. One 5V filament secondary winding powers the 5R4 high B+ rectifier, and another 6.3V secondary winding powers the rest of the tubes in the Ranger, including the 6AX5-GT low B+ rectifier tube.

Transformer Filament Secondary

Filter Choke:
Filter choke LP2 blocks the AC component in the output of the 6AX5-GT rectifier tube and passes relatively smooth DC to the filter capacitor, C78.

A choke input filter lowers the peak current the rectifier tube must handle, and increases the overall average current that the rectifier tube can deliver.

Filter Choke

Filter Capacitor:
The relatively smooth output of the filter choke is additionally filtered by capacitor C78. The capacitor further smooths out the variations in the output of the filter choke to produce pure DC.

Filter Capacitor

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