Most 3-400 amps with a 3-500 swap can be used with the cut down anode
coolers used on Ameritron, Amp Suppy, Kenwood and some other amps plus
currently available aftermarket.
Carl
KM1H
----- Original Message -----
From: "Steven Katz" <stevek@jmr.com>
To: "mike stokes" <mike9v@gmail.com>; "Amps" <amps@contesting.com>
Sent: Wednesday, June 12, 2013 11:01 AM
Subject: Re: [Amps] Swan Mark 1
I'm very familiar with the Mark I. It's not as good as the Mark II. :)
Two potential issues:
3-400Zs haven't been manufactured in over 40 years. 3-500Zs are a direct
replacement, however they are "taller" and the Mark I usually requires
mechanical modification to accommodate the extra tube height. Also, while
the 3-400Z was a "zero bias" tube at 3000V (for AB2), the 3-500Z really
isn't and normally needs a bit of cathode bias to bring the idling current
down to something reasonable. (They'll "run" at zero bias, but dissipate
a lot of power under zero-signal conditions, creating heat etc.)
The other issue is the Mark I has the power supply in the same enclosure
as the tubes. The tubes get very hot (of course) and make the transformer
hotter, so they are prone to failure. I've replaced power transformers in
several Mark I's over the decades - some didn't last more than a few years
(back in the early 70s) before they gave up, if they were used a lot. The
Mark II doesn't have this issue, as its power supply is separate and has
its own cooling system.
But should be a good candidate for a monoband amp.
73
Steve WB2WIK
-----Original Message-----
From: Amps [mailto:amps-bounces@contesting.com] On Behalf Of mike stokes
Sent: Tuesday, June 11, 2013 8:48 PM
To: Amps
Subject: [Amps] Swan Mark 1
Hello
I have an oppertunity to pick up a Swan Mark 1 amp which uses a pair of
3-400s. 10M-80M with no tuned input. I thouhgt it might be a good choice
to convert to either single band 6 Meters or 160 Meters.
Any thoughts are appreciated.
--
Mike Stokes
KK9V
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