If you have a lot of old tubes, then this idea could be useful. I have planned to make this small device, but somehow quite lazy (ugh!). I think because I have Knight 600 and Hickok 539B which are quite convenient to be used.

A background of this idea is, usually an old stock tube, either NOS or not, has been kept inside the box, attic, or warehouse for years. Some could be more than 10 years. Sometime, turn it on with maximum voltage could become a ‘heart attack’ for it. Well, it’s ok if it’s a cheap $2 tube. But how about for $400 RGN?

Usually I use my tube tester, either Knight or Hickok, and set lower filament voltage first for some time before putting an actual filament voltage to this kind of tube. But somehow, I would prefer to have a simple stuff but with more function. Here you go.

The ingredients are simple. Some hole saws (lucky if have quite vary of size). A thick platform or box is nice to have for this purpose (could be acrylic, wood, or metal plate). Some rulers to measure the size. Off course you will need a drill with some extra bits. It’s always nice to work if you have a complete stuffs.

I will not teach you how to do it, but the final result would be like below.

The next step (which I haven’t done) is to connect all the filament of those 4 sockets in parallel configuration. Then, we should connect them into a regulated power supply which voltage can be adjusted (good if it could regulate the current to). Will continue on this later…