Hi Bill et al.
The one I remember was the grid collet for the 8938 on 432. It needed a
slight bit of inductance for best neutralization. I remember that Steve
figured it out, although the amplifier worked fine without it, you would see
some drifting in the power output, no doubt due to some regeneration in the
grid crcuit. After removing a small number of fingers from the grounded
collet, the amplifier was much more stable as far as power output went. When
I got the tube initially, W6PO indicated that it had flunked the stable
power output test and was rejected for an order to the Swiss gov't. The
tubes were for remote unattended sites where the tubes would normally be off
until required and then had to reach full power from a cold start. Bob
indicated that with use the tube would probably improve and be just fine. I
did see power drift, which improved, but, by removing teeth from the finger
stock, it got really stable. Now I do not notice much drift at all. I think
Steve removed every fourth finger. I could always take the 432 KW apart and
look at the grid ring!
Dave K1WHS
----- Original Message -----
From: "Bill Olson" <callbill@hotmail.com>
To: "terry price" <w8zn54@verizon.net>; "VHF Contest Reflector"
<vhfcontesting@contesting.com>
Sent: Tuesday, October 20, 2015 4:48 PM
Subject: Re: [VHFcontesting] 3cx800a 222 amp
yeah, duh, I was talking about the grid collet!! so where I said "cathode
connection" was just me being stupid, what I MEANT was I seem to remember
there needed to be just a little inductance in the grid connection, so
with homebrew collets you had to diddle with the number of fingers a
little..
bill
From: w8zn54@verizon.net
To: callbill@hotmail.com; vhfcontesting@contesting.com
Date: Tue, 20 Oct 2015 12:39:16 -0400
Subject: Re: [VHFcontesting] 3cx800a 222 amp
I've built several 3CX800A7 222 amps and the cathode circuit that was
used
on the 8874 version was the same. The plate line changed.
Terry - W8ZN
-----Original Message-----
From: VHFcontesting [mailto:vhfcontesting-bounces@contesting.com] On
Behalf
Of Bill Olson
Sent: Tuesday, October 20, 2015 12:00 PM
To: VHF Contest Reflector
Subject: Re: [VHFcontesting] 3cx800a 222 amp
Ralph, I'm really straining my brain here, but I seem to remember these
triodes wanted a little inductance in the cathode connection to
"neutralize"
them. I remember with an 8874 on 220 back 35 or 40 years ago I build a
home
made grid collet with finger stock.. The finger stock was in a solid ring
at
first but in order to make the thing work I had to keep bending fingers
away
from the grid ring on the tube.. That's all I remember, don't have that
amp
any more..
Steve, W1SMS, now owns and runs Lunar Link, I'm sure he has the info you
want..
bill, k1DY
> Date: Tue, 20 Oct 2015 11:23:01 -0400
> From: mathenyr@marietta.edu
> To: vhfcontesting@contesting.com
> Subject: [VHFcontesting] 3cx800a 222 amp
>
>
>
> I remember reading that there was a K1FO 222 amp using a single
> 3xc800a7 tube. I have tired to get such an amp to behave without
> success...cathode circuit problems.
>
> Does anyone know if the K1FO amp description was ever published? Does
> anybody have one of the amps who could send me a copy of a manual or
> perhaps photos??
>
> Also looking for a proper grid collet for the thing...
> Eimac 720359 ... anybody know a source? The grid collet
> may be my problem, but I am on my second "hamstyle" version and
> getting frustrated.
>
> The 2M version of the thing worked first try....
>
> Thanks..
>
> de K8RYU
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> VHFcontesting mailing list
> VHFcontesting@contesting.com
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