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Re: [Amps] Tube amps are not a thing of the past

Subject: Re: [Amps] Tube amps are not a thing of the past
From: N1BUG <>
Date: Mon, 5 Jun 2017 14:15:43 -0400
List-post: <>
I just cut the anode off a dud 4CX1000A. The control grid structure cannot be seen until I determine how to cut away the screen grid without destroying the control grid which I am going to guess is not far inside it.

I ran a 4CX1000A with 5 mA grid current on CW at 144 MHz for years. I don't know whether the tube was harmed in any way but this but performance never changed. I had it biased to near cutoff with only about 10 mA plate idling current, but I don't recall what the grid voltage was. I would guess somewhere around 75V. At 5 mA that's still not much grid dissipation!


On 06/05/2017 01:30 PM, Gary Schafer wrote:
Hi Jim,
I think that the 4CX1500 has the same grid as the 4CX1000.
Somewhere I have seen it written by Eimac that it is ok to draw a small
amount of grid current during brief tune up.

The Collins 30S-1 (4CX1000) develops ALC from grid current.

Gary  K4FMX

-----Original Message-----
From: Amps [] On Behalf Of MU 4CX250B
Sent: Monday, June 05, 2017 11:03 AM
To: Jim Thomson
Subject: Re: [Amps] Tube amps are not a thing of the past

I've long wondered what the zero watt rating of the 4cx1000 grid
actually means. I've assumed it means the tube is rated for class AB1
operation only, and that the rating doesn't reflect the actual
physical limitation of the grid structure.  I wonder if anybody has
actually cut apart a tube and inspected the grid?
Jim w8zr

N1BUG  160m-2m         DXCC Honor Roll
WI2XTC 2200m-630m Experimental license
FN55mf      ME      Piscataquis County
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