Archive for October 22nd, 2015

0D3 Voltage Regulator Tube

A quartet of ceramic octal tube sockets arrived from halfway around the planet and matched up nicely with the business end of a 0D3 voltage regulator tube from the Hollow State Electronics box:

0D3 voltage regulator tube in socket

0D3 voltage regulator tube in socket

If the 1-48 on the side of the tube base (facing away in the picture) means anything, then General Electric built it in January 1948.

The pinout view in the datasheet assumes you’re looking at the bottom of the socket, which makes perfect sense given the hand-wired chassis construction techniques of the day:

0D3 Voltage Regulator Tube - pinout

0D3 Voltage Regulator Tube – pinout

So the view is backwards when seen from the top, not that you’d ever need it:

Ceramic octal tube socket - 0D3 pinout

Ceramic octal tube socket – 0D3 pinout

The internal jumper across pins 3-7 allows you to disconnect the downstream circuit when the regulator isn’t in the socket, which is a Very Good Idea with a shunt regulator.

Not having a 200 V power supply ready to hand, but having recently restocked the 9 V alkaline battery box, this actually worked:

0D3 voltage regulator test setup

0D3 voltage regulator test setup

That’s 16 x 9-ish V = 150 V across the battery terminals, plus a 50 V adjustable bench power supply coming in on clip leads from the upper right, with current shown on a digital panel meter across a 1 Ω sense resistor. The classic 1.5 kΩ carbon resistor emerged from from a coffee can of parts that Came With The House™ and seemed appropriate for the occasion.

The tube conducts a few milliamps through a small plasma filament discharge at 150 V. The current ramps up to about 10 mA as the supply voltage increases to 180 V, whereupon the tube fires and the current jumps to 30 mA (which is less than the spec, but I ran the power supply in constant-current mode to avoid whoopsies).

Reducing the current to 10 mA slightly reduces the area involved in the plasma discharge, but the tube still produces a nice display through the mica spacer / insulator atop the plate:

0D3 voltage regulator - 10 mA current

0D3 voltage regulator – 10 mA current

That isn’t quite in focus, but should give you the general idea.

I didn’t measure the operating voltages across the tube, mostly because I didn’t want more cheap clip leads cluttering the bench.

It’d make a very low intensity nightlight that dissipates a watt or two. Boosting the current to the absolute maximum 40 mA would brighten it up a bit, but dissipating 6 W in the tube probably won’t do it any good.

This obviously calls for an Arduino monitoring the tube current with a Hall-effect sensor and regulating it with a hulking MOSFET…