Are you able to tune the grid control for a current peak? Also do the output
controls tune properly or are they at one extreme or the other?
Have you tried to Grid Dip the input and outputs? Id trust that method for
starters instead of the MFJ.
The 847 should blow the pants off an 8877 so its either a building/tuning
error or a bad tube.
What sort of plate idling current do you get (no drive)? around 45-60 ma is
OK.
Carl
KM1H
----- Original Message -----
From: "Hugh Duff" <hduff@cogeco.ca>
To: <amps@contesting.com>; <vhftubeamps@yahoogroups.com>
Sent: Wednesday, May 09, 2007 6:31 PM
Subject: [Amps] W6PO 2m amp
> Hello all !
>
> I'm testing the homebrew W6PO amp that I just completed and I seem to be
> having trouble getting more than 300 watts out of it.
> Before I powered it up I tuned the input and output sections for minimum
> SWR at 144.1 MHz using an MFJ-259 antenna analyzer.
>
> I have the amp connected to an FT-847 exciter and a large Bird dummy
> load. HV is between 2500 and 3000vdc on the plate. I see about 300mA
> current on the plate when I'm getting 300 watts out but very little
> current on the grid meter, which I find a bit odd. I 'm using a G3SEK
> Triode board to provide the bias and control. I do see 12vdc bias on the
> cathode during TX.
>
> The 3CPX1500a7 tube was purchased as a medical pull. I have no way to
> verify its condition so there is always a chance it's no good. This is
> my first big tube amp so I'd like to make sure I'm not doing anything
> wrong before I think about buying another tube.
>
> Any guidance will be appreciated.
>
> (Pix of the amp can be seen at http://www.va3to.com )
>
> Thanks, Hugh VA3TO
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>
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