Was I wasting my time , rather than throwing out some ECC83, a 6V6 and some
EL34 and EL84.? All various degrees of C/H leakage causing
vibration/tinging sensitivity so useless despite useful gain.

All measured 5 to 20 M ohm on C/H insulation test on valve tester.
Decided to power the heaters from a bench ps and try C/H leakage with a 500V
Megger insulation tester.
Increasing the heater volts from normal 6V , for short durations then back
to 6 , and monitoring on the Megger. Eventually taking up to 15V for 1
second , no longer orange glow of course, and vey low C/H Megger resistance.
Now measuring them for the C/H leakage on the valve tester better than 30
meg (maximum measurable on my tester).

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/

On Dec 21, 10:01*am, Meat Plow wrote:
On Fri, 21 Dec 2007 15:51:52 +0000, N Cook wrote:
Was I wasting my time , rather than throwing out some ECC83, a 6V6 and some
EL34 and EL84.? *All various degrees of C/H leakage causing
vibration/tinging sensitivity so useless despite useful gain.

All measured 5 to 20 M ohm on C/H insulation test on valve tester.
Decided to power the heaters from a bench ps and try C/H leakage with a 500V
Megger insulation tester.
Increasing the heater volts from normal 6V , for short durations then back
to 6 , and monitoring on the Megger. Eventually taking up to 15V for 1
second , no longer orange glow of course, and vey low C/H Megger resistance.
Now measuring them for the C/H leakage on the valve tester better than 30
meg (maximum measurable on my tester).

CRT rejuvenators *did something similar but the theory was to strip
dead material off the cathode.

That was to expose new fresh cathode material to increase the emission
of the electron guns, I used them many times in the 1950's and 1960's
when TVs were much more expensive and people would do almost anything
to keep a set running.

It was not to reduce/change/eliminate any heater to cathode leakage.
There were special 1:1 filament transformers available to use with
CRT's that had H-K leakage, these transformers were specially wound
to minimize capacitance between the windings so that if video
information was fed to the cathode, the signal was not degraded by the
windings of the special filament transformer and there was no leakage
to the heater.

Bob Hofmann

"hr(bob) " wrote in message
...
On Dec 21, 10:01 am, Meat Plow wrote:
On Fri, 21 Dec 2007 15:51:52 +0000, N Cook wrote:
Was I wasting my time , rather than throwing out some ECC83, a 6V6 and
some
EL34 and EL84.? All various degrees of C/H leakage causing
vibration/tinging sensitivity so useless despite useful gain.

All measured 5 to 20 M ohm on C/H insulation test on valve tester.
Decided to power the heaters from a bench ps and try C/H leakage with a
500V
Megger insulation tester.
Increasing the heater volts from normal 6V , for short durations then
back
to 6 , and monitoring on the Megger. Eventually taking up to 15V for 1
second , no longer orange glow of course, and vey low C/H Megger
resistance.
Now measuring them for the C/H leakage on the valve tester better than
30
meg (maximum measurable on my tester).

CRT rejuvenators did something similar but the theory was to strip
dead material off the cathode.

That was to expose new fresh cathode material to increase the emission
of the electron guns, I used them many times in the 1950's and 1960's
when TVs were much more expensive and people would do almost anything
to keep a set running.

It was not to reduce/change/eliminate any heater to cathode leakage.
There were special 1:1 filament transformers available to use with
CRT's that had H-K leakage, these transformers were specially wound
to minimize capacitance between the windings so that if video
information was fed to the cathode, the signal was not degraded by the
windings of the special filament transformer and there was no leakage
to the heater.

Bob Hofmann

The B&K CRT rejuvenator that I used extensively in the 80's, had a specific
setting for blasting off H-K leakage, which I believe was caused by material
'bubbling' off the cathodes over the years and forming a high R 'bridge'
across to the cathode cylinders. Not so prevalent a problem in standard
valves (tubes) when used in their 'standard' upright configuration, as
opposed to the normal horizontal configuration of CRT guns, wher gravity
plays a part in causing the contamination to sag across the small H-K gap.
Perhaps the ones that Mr Cook had, were taken from amps that had used them
on their sides ?

Arfa