>
>A friend of mine has aquired a used Titan 425 amp. The amp has seen
>very little use since purchased originally, probably less than 25 hours.
>
>Here is the question:
>
>During tune up on 80 or 160 metres, the amp shows expected grid current,
>but after tune up and after a short pause, the amp will initially show
>high grid current in SSB for the first 3 or 4 seconds of operation,
>after which the grid current returns to where it was on tune up.
>Suspect dilectic heating somewhere, but where? Could this be some other
>problem?
Firstly, I would try to determine if the problem is in the tubes or in
the amplifier. To make this determination, I would test the tubes for
abnormal leakage. To do this you need a +/- 5kV high-pot tester,
current-limited to a couple of hundred uA. . With +5kV on the anode,
you should be seeing under 10uA. If the measured leakage decreases when
the anode is negative, you could have a bit of gold-sputtering -- which
is Not necessarily a fatal condition. Loose gold will definitely mess
with grid-current readings.
cheers, Sam.
- Rich..., 805.386.3734, www.vcnet.com/measures.
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