[Amps] Drifting grid current

[Alek Petkovic]

G'day Martin

You mentioned a black mark on the plate cap but you never mentioned 
the large brown stain in your underpants caused by that flashover.

Try Dr Alex, UR4LL for replacement caps. He is very good to deal 
with. http://www.nd2x.net/ur4ll.html

73, Alek
VK6APK





At 09:33 AM 4/11/2007, Martin Sole wrote:
>Thanks for all the useful thoughts and ideas about my drifting grid current.
>
>It doesn't drift at the moment but that is because it will not switch on
>:'(
>Whilst trying 15M at about 1200 watts it went pop and took out the 1.25A
>fuse in the soft start that the plate over current relay forces back in
>line. Replacement did the same thing. Examination showed the plate
>blocking cap with a large black mark and a small, about 1mm, piece
>missing. I need to source a replacements but hopefully the drifting was
>the plate block overheating and preparing to depart. We'll see.
>
>73
>Martin, HS0ZED
>
>
>
> >
> > ----- Original Message ----- From: "Martin Sole" <msole at loxinfo.co.th>
> > To: <amps at contesting.com>
> > Sent: Saturday, November 03, 2007 9:07 AM
> > Subject: [Amps] Drifting grid current
> >
> >
> >> Having read with interest the recent 8874 thread I am prompted to ask a
> >> question that has been bugging me for a while.
> >> My Alpha 78 with what I believe are 3 NOS 8874 tubes, 2 from one source
> >> third from another does about 1500 watts out key down. Plate voltage
> >> shows about 1800 at that time, about 2150 to 2200 off load. Grid current
> >> runs about 80 to 90 mA but if I key up for a while then key down again
> >> the grid current first registers just over 100mA and then over a period
> >> of a few seconds drops back to about 80mA. Power out does not seem to
> >> change.
> >>
> >> Is it something getting hot? Drifting? Or is it just normal?
> >>
> >> Thanks
> >>
> >> Martin, HS0ZED
> >>
> >>
> >> _______________________________________________
> >> Amps mailing list
> >> Amps at contesting.com
> >> http://lists.contesting.com/mailman/listinfo/amps
> >>
> >
> >
> >
>_______________________________________________
>Amps mailing list
>Amps at contesting.com
>http://lists.contesting.com/mailman/listinfo/amps


http://www.qrz.com/vk6apk