[Amps] Swan Mark 1

[Carl]

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 at jmr.com>
To: "mike stokes" <mike9v at gmail.com>; "Amps" <amps at 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 at 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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