[Amps] DEAD Alpha 91B

[Carl]

----- Original Message ----- 
From: "Paul Christensen" <w9ac at arrl.net>
To: <amps at contesting.com>
Sent: Monday, May 18, 2009 1:06 PM
Subject: Re: [Amps] DEAD Alpha 91B


> >I believe the Alpha 77 series were the last to violate NEC but not 
> >the
>> only company do do so.
>
> As I recall, some of the old Henry amps used chassis ground as a 
> neutral as
> well.  On the Alpha 70 and 77 series, the fix to the amp is easy and 
> doesn't
> even require turning a single cabinet screw.  Neutral and ground can 
> be
> separated by cutting a jumper on the power cord's Cinch-Jones plug. 
> After
> the change, the amp complies with today's NEC.
>
> Of course, the real hassle is in converting one's AC shack wiring from
> 3-wire (L1-L2-G) to 4-wire (L1-L2-N-G).  When I moved to the current 
> QTH, I
> ran 4-wire, #10 AWG from the start.  Pulling that stuff through the 
> walls is
> not a fun process as an electrical re-work project.
>
> Speaking of the chassis-carrying current, I recently modified my Alpha 
> 77Dx
> by adding a filament RFC, thus raising the filament return above 
> chassis
> ground.  I've always detested using the chassis as a 
> high-current-carrying
> conductor.  For a single 8877, that's 10A of AC current.  For the 
> 77Sx,
> that's 20A of current through the chassis.   For me, another benefit 
> was in
> the reduction of filament V as a result of high utility line voltage. 
> It
> went from 5.6V before the mod to 5.0V after the mod due to the slight 
> (but
> needed) IR drop through the new filament RFC.  Arguably, even the 
> newer
> Alpha amps that utilize the chassis as a filament return could 
> probably
> benefit from a filament choke upgrade.
>
> Paul, W9AC


Yep, Henry was the other main culprit, I have a Tempo 2001 in here for 
repair right now that will be corrected.

Carl
KM1H