[Amps] Photos posted of high voltage test setup of a YC-176
rezycle.bin at gmail.com
Fri Oct 21 12:54:04 PDT 2011
I didn't test breakdown between G-C so far. In a grounded grid setup with a tube like this, my understanding is that an A-G arc is the most likely. The grid is a circular cage surrounding the cathode (reference: internal pictures of the YC-159 at http://gs35b.com/yc156/ ). The grid potential will stay very close to B-. I assume therefore that since the potential between G-C will be quite low, the risk for an arc there is low. (Provided the low ohm clamping resistor from chassis to B- is OK). I may of course be wrong.
I have not yet found many references that state that one should do a hipot test from G to C. In studying the Eimac datasheet for the YC-156 http://www.g8wrb.org/data/Eimac/YC156.pdf (YC-156 is same tube as YC-179), I see on page 3 that the maximum G to C peak potential should be 425 volts. This may indicate that one should be careful with applying too high voltages from G to C. If you have more specific information about what voltage the G-C path should hipot test without appreciable leakage current for a good tube, I would be interested in receiving this information.
I agree with your comments regarding unknown heater and grid condition. That I will have to test and cross my fingers.
An alternative may be to check the interelectrode capacitances. That would probably give an indication of misaligned elements inside the tube.
>> I assume I have a good tube when it shows that low leakage at 16KV (DC). Any opinions on that?
> That's assuming a bit too much. I'd say it means you have a good VACUUM, but:
> the filament might be open, or have low emission
> the grid might be damaged from a previous overcurrent event(s).
> the grid might be shorted to the filament.
> But, so far, it looks like you might have a good tube.
> The next thing I'd do is test interelectrode leakage between the other elements.
> Then, I'd see if the filament works, i.e. draws the correct current at the correct
> voltage. If you heat the filament for more than just a few seconds, be sure to provide
> some cooling air.
> Good luck es 73,
> George T Daughters, K6GT
> CU in the California QSO Party (CQP)
> October 6-7, 2012
More information about the Amps