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Re: [Amps] Alpha 78 Problem

To: <K8MLM@aol.com>, <km1h@jeremy.mv.com>, <audioguy@charter.net>
Subject: Re: [Amps] Alpha 78 Problem
From: "Paul Christensen" <w9ac@arrl.net>
Date: Wed, 30 Dec 2009 07:58:22 -0500
List-post: <amps@contesting.com">mailto:amps@contesting.com>
> When the  77 was still in regular use it was easy to spot one by the
> splatter
> caused  by the electronic bias spike. There has been a lot written about a
> fix.

I spoke with Ray Heaton about this back when I purchased my first 77Dx.  On 
the Dx/Sx models, the EBS can be defeated by adjusting one potentiometer on 
the bias board.  Plate idling current can be adjusted to reasonable levels 
and the added heat produced when the key line is pulled low is never a 
problem.

By contrast, my Alpha 70V uses a fixed EBS system and when signal strength 
on the Rx end is very strong, artifacts from the EBS can certainly be heard. 
I have two different modifications for this but decided to leave the 
original EBS intact, at least for now.

Paul, W9AC 

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