Right, Jim. I should have placed a caveat that it's the only right way
without modifying the amp. Knowing most Alpha owners, they would already
scoff at what I've done to my 77Dx amp!
Paul, W9AC
----- Original Message -----
From: "Jim Brown" <jim@audiosystemsgroup.com>
To: <amps@contesting.com>
Sent: Monday, April 04, 2011 12:44 PM
Subject: Re: [Amps] what is a 4 wire 240VAC service?
> On 4/4/2011 9:03 AM, Paul Christensen wrote:
>> So, left unmodified, older amps with 120V blowers are still a safety
>> concern
>> if they are serviced by only 3-wires. There's only one right way: Pull
>> 4-wire, 240/120v service into the shack with proper conductor and breaker
>> size, and replace the 3-wire power cord with a 4-wire power cord. The
>> latter part is easy with Alpha 70/77 series amps.
>
> There's another very good way to do it, as practiced by Ten Tec in the
> Titan 425. The 120V blower runs across one half of the primary of the
> high voltage transformer, and the center tap is not bonded to the
> chassis. There's no good reason to bond the center tap to the chassis,
> and in this case, it must NOT be bonded, because that would cause part
> of the fan current to flow on the green wire.
>
> This configuration is shown in one of the Power Point slides that are
> part of my presentation on Ham Interfacing, also on the website.
>
> 73, Jim Brown K9YC
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