[SADXA] Hi-pot tester and 3-500z tube tester

[k7nx at cox.net]

I have built two pieces of test equipment that may be of interest to the group.

First, I built a "hi-pot" tester that is described on the K8CU web page at 
http://www.realhamradio.com/High_Voltage_Breakdown_Tester.htm

This tester can apply a variac controlled, current limited voltage up to 8000 volts and is non-destructive to the part under test.  I find it very useful to test the voltage rating on air variable caps, vacuum caps, vacuum relays and even vacuum tubes.  If you have questionable vacuum parts in your junkbox, or if you have a box of variable caps you'd like to determine the ratings of, I can help you do that. I believe it will also identify a "gassy" tube, or a potential grid to filament short.

Second, I built "A tube tester for high power transmitting tubes" as described on page 41 of the April 2012 QST.  In my mind, the jury is still out on how effective this tester is although I believe it will verify enough that you can put the tube into an amplifier for a final "smoke test", and be fairly confident it won't damage the amp.  My tester will test 3-500z and 4-400a tubes.  I tested several 4-400s and have picked off a grid to filament short and a gassy tube that was ready to flash.  This tester does light up the filament, has forced cooling, has variac controlled HV up to 3500v and has cathode voltage metering (which I haven't figured what use that is so far.).  Everything is fused and current limited.  The actual current through the tube under test is very low - that's  the only drawback.

If you have "spare"  3-500's or 4-400's that may be bad, or if you have any vacuum devices you'd like to test - I'll be happy to do it for free.  Talk to me at the meeting or send me a note if you'd like to test something.

Lloyd  - K7NX