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Re: [Amps] drake l-4b from 4-400 to 3-500

To: DF3KV <df3kv@aol.com>
Subject: Re: [Amps] drake l-4b from 4-400 to 3-500
From: R.Measures <r@somis.org>
Date: Tue, 24 Aug 2004 07:48:33 -0700
List-post: <mailto:amps@contesting.com>

On Aug 24, 2004, at 7:20 AM, DF3KV wrote:



----- Original Message ----- From: "Partain, Chuck" <Chuck_Partain@maxtor.com>

i'm thinking now, it maybe a L4 not the B model..

maybe i just didn't pay attention...I've been busy with
too many projects. this was given to me to look at for a repair
(yes a friend ham) and was just curious on swapping this over.
the PS had bad caps(replaced) the diodes were replaced and also the
glitch resistor and a 5k 10w was cooked...that had been replaced. so
some work
has been done..


Hi Chuck,

the L4 was equipped with 3-400Z and the L4B with 3-500Z.
If you still get full output there is no need to swap the tubes,
anyway both types will do fine.
Alternatively you could use 4-400s if you wire the screen
connectors to the grid, but they need a bit more drive.
Mine doing very well in my L4B

- However, in order to get enough ZSAC in a 4-400 with zero V bias, one needs c. 3500vdc on the anode - or apply a small positive voltage to the screen with a lower anode supply V.

73 Peter

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Richard L. Measures, AG6K, 805.386.3734. www.somis.org

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