145 Volt Regulated Power Supply for Tube Circuits


(click on any picture to see larger version)

NOTE: 'N5FC' is my former call.
This project was constructed while that call was valid, and you may observe references to it.

I've been wanting to homebrew some tube equipment for some time. When it comes to power supplies for homebrew gear, solid state projects can often get away with a 9 volt battery... not so with tubes. I wanted a power supply that would serve to power a QRP tube transmitter (like my Altoobs rig), or a two or three tube receiver. This little power supply will serve both. I also wanted it compact, and at 5.5 x 4 x 3.5 inches, I think I succeeded.

The circuit utilizes a fullwave rectifier following a small (15VA) 115V:115V isolation transformer. After some RC filtering, we have about 165 VDC with moderate ripple. A simple but effective solid-state regulator circuit, utilizing two sweep-amplifier transistors, reduces ripple to less than 0.1 %, and provides about 145 VDC regulated output at up to 75 mA. Load regulation (no load to full load) seems to be around 2.5%. This should make an excellent supply for our cathode-keyed transmitter (the regulation should help minimize key clicks), and be quite adequate for a simple tube-based receiver.

And of course, we have another transformer capable of supplying 12 or 6.3 VAC at up to 1 amp, for filaments.

Here's a crude working schematic of the power supply:


(click on the image above for a larger, semi-clearer version)

The PC boards were constructed using the "cut-and-peel" method, whereby one uses a hobby knife to renmove unwanted copper, and form islands.

CAUTION! Always wear safety goggles when using a hobby knife!

Here are some more images, showing various construction details:

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