[Amps] 220V service for amplifier

[Michael Tope]

Jason,

I ran into this problem with the Henry 2K-D that was donated
to our local club station. Even when operated from a 240VAC
circuit, the Henry still requires 120VAC from the mains
to run the blower and the filament transformer. The Henry
picks this voltage up between one phase of the 240 VAC
circuit and the system "neutral". A fourth connection is made
between the amplifier chassis and the electrical system safety
ground (e.g. the "green wire"). As was mentioned in another
posting, this "green wire" connection exists soley for purposes
of electrical safety and normally doesn't carry any current. A
proper 240 V connection to the Henry requires a 4 wire 240
VAC circuit. Two hots, a neutral, and safety ground. A 3 wire
240 Volt connection won't work because it doesn't include a
neutral connection. In this case, you can tie the neutral and the
safety ground together at the amplifier and "share" the third
green safety ground wire in the 3 prong mains plug. This will
work as long as you don't have any ground fault interrupters on
that circuit, but it is NOT COMPLIANT with NEC. In this
configuration, if you have a fault in your current carrying
neutral/safety ground connection, your chassis will be sitting
at 110 VAC above ground potential ("ouch").

On the other hand, if the Centurion power plug only requires
three wires, then most likely, it doesn't require a neutral
connection to get 120 VAC and 240 VAC from the mains
at the same time. Our clubs Alpha 78s and my Drake L-7s are
all configured this way. They don't require 120 VAC and
240 VAC from the mains simultaneously as does the
Henry 2K-D (they get the 120 VAC from the center-tap
of the HV transformer primary).  If this is the case, then you
can safely use a three wire 240 VAC source. One of the
wires from the Centurion power cable will be tied to the
chassis. This wire should be connected to the safety ground
pin on the three-wire 240 VAC mains plug. Each one of the
remaining two wires would then go to the one of the two
remaining "hot" phase connections on the three wire 240
VAC mains plug. In this case, there is no connection to the
AC mains neutral. If you tie an amplifier like this (e.g. one
with a 3 wire 240 VAC power connection) to a 4 wire mains
circuit, then all you have to do is leave the connection to the
mains plug neutral open.

73 de Mike, W4EF.....................................................


----- Original Message -----
From: "Jason Buchanan" <jsb at digistar.com>
To: <amps at contesting.com>
Sent: Monday, December 01, 2003 7:19 PM
Subject: [Amps] 220V service for amplifier


>
> I did some searching through the list but haven't managed to hit the
> nail right on the head yet...
>
> For wiring a Ten-Tec Centurion amp to 220V, are there any recommended
> plugs and outlets to use?
>
> I am thinking about using a 3 or 4 prong clothes dryer outlet and plug
> combination for quick/easy disconnect, however the thing i'm wondering
> about is where the neutral and ground tie together, since i'm fairly
> sure that the Centurion doesn't have a 4 wire power cable running out of
> it.  Maybe i'm wrong (probably am wrong).
>
>
> Any help and advice how to properly wire the amp would be greatly
> appreciated.
>
>
>
> thanks,
> Jason
>
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