----- Original Message -----
From: "Paul Christensen" <w9ac@arrl.net>
To: <amps@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
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