Scraps,

Those 1/12A & 1/24A diodes you described are metal stack rectifiers made by STC (Standard Telephones & Cables) for the PMG department. These were used in telephone, switchboard & exchange equipment. There is a brief reference to the 1/12A in a stock list in the PMG Substation Equipment handbook.

Cheers.

I figured they were probably diodes but I haven't seen this type before, they look like a stack of washers. The 1/24A supplies the test voltage, the 1/12A is connected to a 160v tap on the transformer but isn't connected to anything else. No idea what this was for. Does it say what year the handbook is from?

D^D markings, PMG diodes and a University front panel? It's a strange beast but works well for what it is. I seem to remember reading that telephone and switchboard techs were the masters of wire lacing. This tester's got some beautiful lacing in it. It might be something a PMG tech built for himself out of bits and pieces.

You forgot to mention also a Weston meter!

I too thought your tester may have been knocked up by a PMG tech.

The handbook is from 1965, but is in binder form for updates. The page refering to 1/12A is from 1959 & gives a serial number of 285, item number 15.

Cheers.

Looks like your tube tester is similar to this one I have:
With this emissions tester, I found a quick and dirty way to screen large piles of tubes. Separate them by heater voltage, and set the heater voltage selection accordingly. Set the sensitivity control to around 35. After the tube warms up, rotate the selector switch through all positions, and you should find the cathodes or grids or plates. Most regular tubes should make a good reading. Tubes that seem weak should be more carefully tested later.

My tester doesn't have a heater pin selector switch, but there are a few duplicates of the same kind of tube socket but with differing heater wiring. With yours I'd just set the heater pin to pin 4 to do 7 and 9 pin miniature tubes. And set your sensitivity to around 25.