Gary - I agree with Carl - looking at the Eimac constant current curves -
those tubes look fine. 175 ma at zero bias and about 3100 volts is what it
ought to be.
I still think you have a blown bias transistor or transistors or the 8.2 v
zener is shot too. Fig 5-31 Filament- AC board
If you talked to Garry Green at TT ,I am surprised he did not say the
same. Incidentally , there is an error on the 81537 board drawing , Fig 5-31
Filament- AC board , where it says to plug 14 on QSK board , it should say
to plug 22 on qsk board.
Also as a help , the wires to 22 on the fil board are orange , and are white
to 21. K is the heavy lead to CT of filament transformer ( fils of
3-500's. ) If I remember right you can unplug those two wires and get to the
junctions of the TO3 without removing the board.
73 hank K7HP
----- Original Message -----
From: "Gary Smith" <wa6fgi@sbcglobal.net>
To: <amps@contesting.com>
Sent: Wednesday, June 09, 2010 4:35 PM
Subject: [Amps] Centurion plate current issue
> Hi to the group:
>
> Finally got around to taking off the cover (excess of twenty screws)
> removed both tubes from sockets and switched the amp on. No plate current
> draw. Good. Was suggested by TenTec to insert tubes one at a time and
> check plate current.
>
> Did that, plate current draw with either tube in place is 175 ma or so.
>
> Is there any way to check (with ohmmeter) for internal shorts? Which pin
> to what particular pin?
>
> I `spose anything is possible but both tubes going bad at same time?
>
> When checking the tubes, had the HV on for maybe no more than 30 seconds
> or so, aluminum heat dissipaters on the tube(s) was extremely hot to the
> touch.
>
> Fwiw, tubes are RF products house brand. If I need new ones, any
> difference form RF house and Taylor's?
>
> looking of some ideas on this one (some more),
>
> 73, Gary...wa6fgi
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>
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