[Amps] Alpha 78 Problem

[Carl]

Im aware of that part Paul. I was referring to a fix that allowed the EBS to 
still be used. Its been a long time and I dont remember the details but it 
didnt come from Alpha. It might have been in HRM as that was about the only 
technical mag at the time.

Carl
KM1H

----- Original Message ----- 
From: "Paul Christensen" <w9ac at arrl.net>
To: <K8MLM at aol.com>; <km1h at jeremy.mv.com>; <audioguy at charter.net>
Cc: <amps at contesting.com>
Sent: Wednesday, December 30, 2009 7:58 AM
Subject: Re: [Amps] Alpha 78 Problem


>> 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