PAUL M. PLAYFORD wrote:
>
> I just obtained a Henry 2K-3 that has been in storage for about 5 years.
> I also vaguely recall that you should apply filament voltage without
> the high voltage to 'cook' the tubes if they have not been in service
> for awhile.
> The tubes are a pair of 3-500Z's. Anyone have any thoughts on how long
> I should cook them before I apply the high voltage?
>
> Thanks
> de Paul
Hi Paul,
I would be more worried about the power supply blowing up from age than
the tubes. The 3-500 is a instant on tube and a time delay is not
important. Assuming the amp does not have a time delay, the tube would
return to its bad condition later and still give problems, assuming it
has leaked and heating it up did work. It will not hurt to warm it up, I
have found that in Tetrodes about 1 minute usually does the trick,
watching the resistace increase while it is warming. If you have a ohm
meter with a meg ohm scale simply read between the elements with the
tube on the work bench. There should be zero deflection on the meter.
Since you have two you can compare the readings if any.
If it was me, I would pull both tubes and turn on the Power supply
first and leave it on for a couple of hours. If nothing blows install
the tubes back after making the described check and go for it. That way
if something goes bad you will already have it narrowed down. Depending
on the readings and you find one showing some defection you might want
to insert one tube at a time putting HV on one of them at a time.
Good Luck
Ron W4WA
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