[Amps] Alpha 78 Problem

[Paul Christensen]

Carl,

Not sure myself.  Both mods I have in the files were drafted by prior 70V 
users but they look well-designed.

Paul, W9AC
.

----- Original Message ----- 
From: "Carl" <km1h at jeremy.mv.com>
To: "Paul Christensen" <w9ac at arrl.net>; <K8MLM at aol.com>; 
<audioguy at charter.net>
Cc: <amps at contesting.com>
Sent: Wednesday, December 30, 2009 9:08 AM
Subject: Re: [Amps] Alpha 78 Problem


> 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
>
>