[AMPS] Titan 425 Question

[measures]

>
>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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