[AMPS] 240VAC Amplifier Wiring

[Paul Christensen]

Chuck,

In your case, it appears you ran a neutral, but you are not using it with
the Henry.

I just pulled my Alpha 77Dx manual again.  Vic's concerns relating to an
open neutral are even more apparent when one reviews the 77Dx's AC wiring
diagram.  In what is referred to as their "grounded neutral" configuration,
the chassis ground terminal is JUMPERED to the neutral terminal.  If the
neutral, opens, the chassis is subject to one phase high potential through
the blower (see note below).  In their "no neutral with ground"
configuration, the chassis terminal is separated from the neutral terminal
and the source power ground is connected only to the chassis.

It seems to me that the neutral should ALWAYS be separated from the chassis
and allowed to float above it with the chassis being at true ground
potential through a dedicated ground wire back to the load center (although
the two are at the same potential back at the load center).  Therefore, in
the case of running a neutral, wouldn't it make best safety sense to run a
4-conductor power cable (3-conductor + ground) and:

1) Break the jumper between neutral and chassis ground in the amplifier
2) Run the neutral to the amplifier's neutral terminal (for the amps blower)
3) Run ground to the amplifier chassis.

All DC circuits are chassis ground referenced.  Interestingly, the only AC
chassis ground/neutral requirement is that of the 120 VAC blower (no 240VAC
taps).  If the blower were 240VAC in the first place, I suspect no neutral
would be required and I wouldn't be presenting this for discussion!
Nevertheless, without further modification to the amp, the steps as I just
outlined above seem the most prudent in moving forward.

-Paul, W9AC


----- Original Message -----
From: "Chuck Counselman" <ccc@space.mit.edu>
To: <amps@contesting.com>
Sent: Tuesday, November 14, 2000 11:23 AM
Subject: Re: [AMPS] 240VAC Amplifier Wiring


>
> Paul Christensen W9AC <paulc@mediaone.net> wrote:
> >...Have any of you successfully tried configuration #3, also assuming
there may exist a 4-pole 240VAC plug/receptacle?
>
> The local electrician had installed a four-pin (two phases, neutral, and
ground) outlet in my shack, but when I got my Henry amp., its line cord had
only three wires, which were for the two opposite phases of 240 VAC and a
chassis/cabinet ground.  So I installed a three-pin plug on the cord, having
just these three pins/blades, and no neutral pin.  It was a universal sort
of plug that I found at Home Depot.  It had a nice big sturdy molded nylon
shell and an assortment of pins/blades that you could insert or not.
>
> -Chuck W1HIS
>
>
>
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