This scheme makes no sense to me. It is known a 3-500Z tube has it's
getter on the plate. So if you place 45 volts on the plate and draw 400
ma, you have a plate dissipation of 18 watts. 18 watts is not even
close to getting the plate cherry red. In fact it won't get the plate
to glow at all. Since the plate is the getter and it can't getter
unless the plate is glowing, how in the world can this scheme work?
There is something wrong here. This scheme is telling us the getter
works without a red hot plate. This is news to me as every other
gettering scheme I have seen insists on getting the plate to glow.
Lee, w0vt
On 8/8/2015 10:59 AM, Mike Tubby wrote:
If the 3-500Z has stood for a long time unused I suggest you use the
'Reactivation 3-500Z' procedure by PA0FRI, here:
http://pa0fri.home.xs4all.nl/Lineairs/TL922/tl-922eng.htm
When I did this with a new-old-stock tube I used 40V and had no
significant current indication for about 1.5 days, then the current
meter started to 'flick' a few milli-amps and back to nothing and then
after a few more hours it started a constant reading of around 50-60mA
which then rose until it hit my current limit.
I used a pair of 0-20DC bench power supplies in series to get 40V and
set the current limit at 400mA.
After the reactivation I put the tube in a PA and it worked fine.
Mike G8TIC
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