2 hots, 1 neutral and 1 ground. Not really the proper term though. It's
more properly named 120/240 single phase. With 120/240, you need a neutral.
And a ground of course.
73
Jim W7RY
--------------------------------------------------
From: "Charles Harpole" <k4vud@hotmail.com>
Sent: Sunday, April 03, 2011 7:57 AM
To: <w9ac@arrl.net>; <at6c@bellsouth.net>; <amps@contesting.com>
Subject: [Amps] what is a 4 wire 240VAC service?
>
> Maybe being in Thailand, where 230vac is supplied with TWO wires, makes me
> ask.... what is 4-wire 240vac service?
>
> Charles Harpole k4vud@hotmail.com
>
>
>
>> From: w9ac@arrl.net
>> To: at6c@bellsouth.net; Amps@contesting.com
>> Date: Sun, 3 Apr 2011 10:35:01 -0400
>> Subject: Re: [Amps] Alpha vs Henry
>>
>> George,
>>
>> If 160m is of interest to you, may want to re-evaluate Henry amps,
>> including
>> the 5K.
>>
>> Concerning mods for the 77Dx/Sx: few mods have been published and either
>> version of the 77 is fine as it is. I own a 77Dx and have avoided a
>> conversion to the Sx for several reasons:
>>
>> 1) Added cost of an 8877 during replacement;
>> 2) Slightly added difficulty in isolating trouble with a pair of tubes. A
>> minor issue;
>> 3) The added class of power really requires changing the RF output
>> connector
>> to a DIN type;
>> 4) Fuse holders should be upgraded;
>> 5) Relatively poor Ep regulation of the Sx version unless an outboard
>> Hypersil transformer is used. Some folks have reported better regulation
>> with a direct- replacement Dahl type although it's a snug fit;
>> 6) The Dx already has way more reserve than needed for most operating
>> modes
>> in American-licensed service.
>>
>> Added together, I just can't justify the change. However, I did make the
>> following changes to my 77Dx:
>>
>> 1) Isolated neutral from chassis ground. As it stands, these Alpha amps
>> are
>> not UL compliant. Although not compliant with the NEC, the NEC is
>> factually
>> a premise wiring standard -- not a product wiring standard. The mod is
>> super-easy since it involves only cutting a jumper on the Cinch-Jones
>> power
>> plug. However, 4-wire service and 4-wire power cord is required. If you
>> have not already added 4-wire 240V service, consider it if you plan on
>> using
>> older Alpha and Henry amps;
>>
>> 2) Elevated the filament return off the chassis. I detest the chassis
>> being
>> used for high-current filament returns -- even more of a concern with the
>> Sx
>> as 20A of current flows in the chassis. It's a personal bias of mine;
>> many
>> Alpha amps have run for decades without issues;
>>
>> 3) Added a filament choke. A side benefit is that there's just enough of
>> an
>> IR drop through the choke as a result of my 250VAC mains to ensure that
>> the
>> filaments run at 5.0V. Before adding the choke, my filament voltage ran
>> above Eimac's specification and I was replacing tubes way too often
>> because
>> of filament issues. High filament voltage combined with many intermittent
>> on/off cycles leads to these failures. Also, after inclusion of the
>> choke,
>> I did not tie the filament to the cathode (e.g., AL-1500) although that
>> could be done if I were convinced of the necessity. I've seen arguments
>> both ways (primarily fault related) from respected amp designers as well
>> as
>> former Eimac engineers. It stays unconnected for now;
>>
>> 4) Added gas discharge tubes to the filament and cathode terminals, and
>> added bypass caps to the filaments connections.
>>
>> Just my $0.02, and I'm sure others will disagree with me on some of these
>> changes. Good thing I'm not writing article for QST!
>>
>> Paul, W9AC
>>
>> ----- Original Message -----
>> From: "George Steube" <at6c@bellsouth.net>
>> To: <Amps@contesting.com>
>> Sent: Sunday, April 03, 2011 7:58 AM
>> Subject: [Amps] Alpha vs Henry
>>
>>
>> > Looking at purchasing an Alpha SX/DX or Henry 5K for my amp collection.
>> > Any
>> > advice/comments on these amps would be appreciated. My biggest concern
>> > with
>> > the Henry would be future tube replacement. Any recommend mods for
>> > either
>> > amp? Thanks.
>> > George
>> > W2GS
>> >
>> >
>>
>>
>> --------------------------------------------------------------------------------
>>
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