Here's one that I have made a mock-up on at different times for the fun of it. But I didn't get a very high test voltage.
Bill

What ac voltage do you measure at the xfmr's high-voltage secondary winding? It will depend on the winding ratio.

If you have a 'scope, look at the waveform between the two test probes. It should be a pulsating, rectified wave. What's the peak?

Hi Doug,
I don't recall. Whatever transformer I had at the time as close to the high suggested in the article. I used alligator clip leads didn't hard wire it just to see how it would do. I do remember the 01A looking much brighter with the 6.3 volt filament. I may try it again someday. But I have four cap testers with the tuning eye, that's enough.
Bill

:What ac voltage do you measure at the xfmr's high-voltage secondary winding? It will depend on the winding ratio.
:
:If you have a 'scope, look at the waveform between the two test probes. It should be a pulsating, rectified wave. What's the peak?
:

The filament of an '01A is rated at 5V, so at 6.3V it will run brighter. Probably wouldn't affect tube life all that much, particularly for itermitent use in a cap tester.

When rejuvenating '01As (which have thoriated cathodes), I typically run the filaments for several hours above 6.3V.

A good capacitor should light the neon light no more than once. Any flashing at all indicates leakage. A good capacitor with no leakage might not flash the lamp at all, depending on the situation of power-up. About the only thing this tester is good for is testing for leakage. I wouldn't rely on it for indicating opens. Still, since capacitors rarely open up, it could come in handy. Leakage is what causes most of our troubles.

T.

By the way, after a cap is tested with that device, the cap will be charged. Unless you discharge it, you may get a nasty shock.

:By the way, after a cap is tested with that device, the cap will be charged. Unless you discharge it, you may get a nasty shock.
:
Bill

As a kid, I worked in a filling station that did minor tune-ups: points, plugs, etc. We had a high-voltage cap tester to test ignition condensers. It was great fun to charge up a condenser, and toss it to somebody, saying,"Catch!"

Yes, and with experience you can estimate the cap's value, uF.

:And if a big enough zap you can conclude the cap is good?
:Bill
:

Good point. If an old filter cap can hold enough of a charge for an hour or so, it's probably usable. I use an ancient Eico 950 B to test and reform equally ancient capacitors, and you get a good sense of whether you have a lost cause or not after a few minutes. With patience, it might take a couple of hours or more to reform a really old specimen.

When I am in a rush, I just connect a HV source of the suspect component's rating through a 10 K resistor and dc milliamp meter in parallel, and watch the current consumption.

In the end, it is probably more cost effective, (if your time is worth more than half the minimum wage to just replace the capacitor.

But then again, if you are going to disguise your repair, you will spend a lot of time sawing or melting out the old innerds and stuffing with new components.

Up to you.

:Yes, and with experience you can estimate the cap's value, uF.
:
::And if a big enough zap you can conclude the cap is good?
::Bill
::
:

Hi

You can get an idea of capacity by dumping the charge into a meter with series resistor. The higher a meter reads and longer it hold the more capacity. Need to try it to see the response.

Norm

:Good point. If an old filter cap can hold enough of a charge for an hour or so, it's probably usable. I use an ancient Eico 950 B to test and reform equally ancient capacitors, and you get a good sense of whether you have a lost cause or not after a few minutes. With patience, it might take a couple of hours or more to reform a really old specimen.
:
:When I am in a rush, I just connect a HV source of the suspect component's rating through a 10 K resistor and dc milliamp meter in parallel, and watch the current consumption.
:
:In the end, it is probably more cost effective, (if your time is worth more than half the minimum wage to just replace the capacitor.
:
:But then again, if you are going to disguise your repair, you will spend a lot of time sawing or melting out the old innerds and stuffing with new components.
:
:Up to you.
:
::Yes, and with experience you can estimate the cap's value, uF.
::
:::And if a big enough zap you can conclude the cap is good?
:::Bill
:::
::
: