Hello Jos,
Thanks for answer.
The GU74 are NOS, never used, and were stored inside protective plastic buble
bag.
Did not see traces of dirt and I usually try touching them as less as possible,
because
traces of fingerprints may remain on the ceramic and more on the metal parts
coating,
especially for the new shining tubes. Tinned wires or solder may leave obvious
traces on the ceramic surface also.
Anyway, will try cleaning the ceramic insulation using isopropylic alcohool and
will test them again when time available, as your suggestion may be correct.
But my biggest "?!" is that while it seems that some other amateurs are
using hi-pot tester, they had not observed that behaviour or no feedback about
it.
Maybe they were limited for testing the leakage current only and they don't push
the
test voltage further?!
Or the western tubes are already processed this way at the factory and the
russian
ones are not? Will see further, as I have two more NOS 4CX1500B and more
8122s untested yet...
My friend YO3FG here confirmed me again that sparks were produced inside
the SRS551 low power glass tubes at the first use only, then all ok.
And no damage during that.
73,
Traian
on4kj wrote:
> A very old story.
> Long time ago in the early sixties, we constructed Amps with a
> coaxialcavity on UHF 70 cm . We where happy with 4X150A pulls from the army.
> We had often extern flash over, inside the cavity, these samples where
> throwed away. Untill we find out that tubes which had been cleaned with
> alcohol to get some greas of, they never flashed. Even manipulating the
> tubes with dirty hands can produce some external flashs over.
> Its a very old story.
> Could be Ham hands are cleaner nowadays hi hi .
>
> Jos on4kj
>
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|