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Re: [Amps] 3CX800 grid collet or SK1900

To: <>, <>
Subject: Re: [Amps] 3CX800 grid collet or SK1900
From: "Dick Hanson" <>
Date: Mon, 15 Jun 2015 10:50:14 -0500
List-post: <">>

I know in the Commander 2m single 3CX800 amps, the grid collets used had a
full complement of 'teeth'.
In other words, there were many contacts all around the collet.

Same deal for the K1FO (Lunar) 6m and 2m amps.

On the 70cm Lunar amp, some contacts had been removed to create a
'calibrated' amount of feedback.

Interesting thread.

Dick, K5AND

-----Original Message-----
From: Amps [] On Behalf Of Gerald
Williamson via Amps
Sent: Monday, June 15, 2015 10:41
Subject: Re: [Amps] 3CX800 grid collet or SK1900

Hi Steve, you may well be right about grid inductance not being needed at
2m. It could be more for saving some costs. 
This was the method used in the original Eimac published design by W6PO back
in the early 70's. The Eimac 8877 socket from that era and maybe still
today, used four grounding clips.
I have a 2m coaxial cavity amplifier that uses an 8877 with a continuous
fingerstock ring for grounding the grid. I never noticed it was in need of
neutralization so perhaps it simply does not matter which grid grounding
method  is used on 2m and lower frequencies.
Gerald K5GW
In a message dated 6/15/2015 10:18:39 A.M. Central Daylight Time, writes:

The grid  ring on a 3CX800 is the same size as the screen ring on a
4CX250 so you  could dismantle a '250 base to get one.

I've done neutralising with  grid fingers at UHF but not seen it needed at


>  Hi Conrad, the four finger grid grounding may be there for the 
> purpose
> neutralizing the plate to cathode feedback path.
>  Sort of like you may have seen individual fingers removed from
> to create a small inductance from grid to  ground.
> I have seen many 8877 2m amplifiers that use this  technique.
> 73,
> Gerald  K5GW
> In a message dated  6/15/2015 7:09:42 A.M. Central Daylight Time, 
>  writes:
> I have a  grounded grid 3CX800 2m amplifier that  needs some TLC. One 
> of
> most  alarming things is that the grid  is grounded by 4 small pieces 
> of fingerstock  that has seen  better days.  I thought that I would 
> remedy
> situation   and so I am looking for a grid collet or the SK1900 assembly. 
I have
>  just  moved to the Netherlands and as yet have not learned where I 
> can
> suitable  fingerstock that can be formed into a  rig.
> Any help would be  appreciated.
>  73
> Conrad  PA5Y

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