W5DXS - Heart Of Texas DX Society


KC5LDO 6X4 Power Supply

  The power supply shown is of common design using a 6X4 full wave rectifier with choke filtering. I built this project to power the 6AQ5 transmitter and to supply B voltage for the Hartley transmitter. With the components used in the schematic, it provided 245 VDC for the plate and 6.3 VAC for the 6AQ5 filament. By choosing the correct transformer this design can also be used to power other projects.

  While this P/S was under construction, I noticed that my transformer had a center tap on the 6.3 secondary. Since the Hartley's type 27 tube requires 2.5 VAC for the filament, I wondered if I could make the 6.3 V center tap work. Measuring the voltage between the 6.3 V secondary leads I measured 3.1 volts. A bit high for the 27 tube.

  Once the P/S was finished I connected the Hartley and measured filament voltage at the pins of the 27 tube. It was a bit high at 2.9 volts. After giving some thought, I decided to try a trick I had almost forgotten about.

  By experimenting with different lengths and gauge of wire between P/S and the Hartley, the problem was solved. Using 20 ga. stranded wire cut to 42 inches, I brought the filement voltage down to a 2.5 volts for the type 27 tube. The two wires had the right amount of resistance to lower the voltage.

  The transformer I used came from a junked Webcor reel to reel tape recorder. Unfortunately, there are no numbers stamped on it, so I was unable to locate the manufacturer. It had powered four 6.3 v filaments, so I knew the secondary 6.3 v windings would handle my amperage requirements. At some point in the past I had read that one inch of laminate in the transformer was good for 40 to 50 ma. I'm sure this is a guess, but mine measured 1 1/8 inch and was worth a shot. After testing with the Hartley and 6AQ5 transmitters, the transformer runs warm, but never hot. I suppose I got lucky. Hi Hi

  I am very pleased with one P/S being able to supply 245 VDC, 6.3 VAC and 2.5 VAC.

  High voltage tube power supplies can be dangerous and lethal if caution is not observed. Seek qualified help if you are not familiar with high voltage supplies.

  73, James, KC5LDO

Articles written by James Tobola - KC5LDO
and reproduction, publication, or duplication of this article, or any part thereof,
in any manner is prohibited without the express written permission of the author.

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From the HOTDXS Workbench - How To Build It Yourself

SPC Tuner

Power Generator

One Tube Receiver

Portable Vertical Antenna

1929 Hartley Transmitter

6L6 Transmitter

5U4G Power Supply

AC-1   6V6 Transmitter

6AQ5 CW Transmitter

Pi Network Tuner

6X4 Power Supply

Type 80 Tube Power Supply

6SL7 Twinplex Regenerative Receiver

L - Network Tuner

6AH6 Electronic T/R Switch

R-390A Rack Mount Speaker

Straight Key Gallery

Equipment Rack

6DQ6 Transmitter

Buck Boost Transformer

T - Network Tuner

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