Welcome to my DIY tube tester site!
Above you will see a picture of the
tube analyzer that is the main subject of this site. (I have since added a
scope and an amplifier with headphones). I am currently getting ready to put together the curve tracer
portion which will interface with a PC giving me the option of plotting,
saving, and printing all sorts of graphs! The next step, before the tracer is finished, will be to replace the Fluke 8000A (the main test meter) with an HP 3455A (in storage...somewhere) giving all of my measurements that much more accuracy.
Further plans involve adding three other regulated variable power supplies, each capable of 1000V at 500mA. I have to get the tubes for two of them (16 6550s!) and finish repairing the control circuit on the precision Fluke. (The Fluke will become my main supply when it is finished, as it is capable of resolutions down to .01V!) With this addition will go another test board specially made for high voltage/high current (where a single socket is connected at a time instead of many as per the receiving/light transmitting version you see on the site), an adjustable cooling fan assembly, and a high power variable dummy load all for the testing of large transmitting types. I am in the process of collecting various transmitting tube sockets and will begin setting things up as soon as I have collected about 20 good sockets. The curve tracer will be built with the transmitting portion in mind, capable of a staggering 3600Vpp! Wouldn't it be great to get real curves for that pile of 833's and 211's? Not to mention all of the other weird and wonderful transmitting stuff lying around!
Other improvements could include a noise analyzer, low frequency spectrum analyzer (which could easily be implemented in software alongside the tracer), and maybe, one day over a very long rainbow, a proper jig for measuring microphonics.
The reason I took on such a project
was that I have been frustrated by the lack of a reliable, reasonably priced,
and thorough tube testing devices…and I had most of the parts lying around the
shop. I don’t see a single impediment to the implementation of such a tester
commercially, which really drives me nuts! I also wanted to go a bit farther, having the ability to test most tube parameters (with the exception of capacitance; this is something that would require a lot more work for what I feel is a very minimal return) on both receiving and transmitting tubes.
What that means is: Precise readings, at data sheet specifications, of gain, transconductance, and by calculation plate resistance; heater, cathode, grid, screen, and by calculation (or measurement) plate current; then power output and grid cutoff voltage. I also wanted precise (actual!) measurements of gas current and leakage resistances. In addition, when a circuit is setup, I want to be able to listen to it for microphonics and noise. A tall order? Not really - just a lot of switches, wires, and sockets.
