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[email protected] pfjw@aol.com is offline
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Default HP 54111D dim display

On Friday, January 5, 2018 at 10:01:46 AM UTC-5, Terry Schwartz wrote:
The only zapping process I knew of was used when there were shorted elements in the tube. It can't be done with a tube tester -- rather a charged cap. It can restore emissions, depending on what was shorted in the tube. Heater voltage was not required. If it works, the picture is not typically affected. But too often the short cannot be removed. In fact sometimes it welds an intermittent short permanent.

NT: I'm curious as to your understanding of the process you described -- what is the mechanism that would be in play that would increase emissions by zapping it while powered? Emissions are largely a function of the cathode quality (useful remaining life) and unless a zap removes a cathode short, I don't see how it works. Also don't understand how it would contribute to smear, or how the emissions would fall again, unless the cathode was already bad, in which case the emissions would not have recovered at all.

Terry



Agreed.

I have used charged caps on three occasions (two successful) to restore bad coils in field-coil speakers. I have tried it several times without any success to 'save' open transformer windings.

But, otherwise, 'rejuvenation' for tubes has consisted of over-voltage on the filament for varying periods of time and at varying percentages over what is rated - and not much more. And CRT "Brighteners" increase voltage to the filament in my experience as well. Some by a variable (adjustable) amount as well. Perhaps NT is conflating different processes?

Peter Wieck
Melrose Park, PA