[UK-CONTEST] Cooler is better

[Cooper, Stewart]

Hi Paul,
My old Collins 30S1 has a tumble drier flexi-hose and a very powerful fan pulling air in through an open window when in use.

On another subject...
Has anyone got any idea if the provisional IOTA results are available yet?

Thnaks,

Stewart
GM4AFF

-----Original Message-----
From: uk-contest-bounces at contesting.com
[mailto:uk-contest-bounces at contesting.com]On Behalf Of Paul Beecham
Sent: 12 October 2005 11:17
To: G3SJJ; UK Contest Reflector
Subject: Re: [UK-CONTEST] Cooler is better


Hi all, I run 2 Acom 2000's and in the heat of battle the shack soon heat's
up. Instead of installing  auxilliary fan's I've put 2 shower fans in the
cavity of an outside wall at floor level and put the amp's air inlet
directly behind them. They run really cool and get a constant suuply of
fresh air. This of course won't suit all applications but it's good for me!
pictures of this at
http://g6pz.magicbug.co.uk/gallery/Shack-Photos?page=1  73 Paul G6PZ
----- Original Message -----
From: "G3SJJ" <g3sjj at btinternet.com>
To: "UK Contest Reflector" <uk-contest at contesting.com>
Sent: Monday, October 10, 2005 10:47 PM
Subject: [UK-CONTEST] Cooler is better


> After the Convention Dinner and YOX's superb quiz on linear amps
> (disappointed not to have won that!) jut thought Reflectees might like to
> see this note from the Acom Reflector. Double edged sword really. The
Yanks
> did the East a favour by forcing them to make "real" amp tubes with the
> downside side of a long wait before you get to the meat!  Chris G3SJJ  :
>
> Interesting to find there seems to be two ways to wire the aux fan.  I
> wired mine in - put the wires on the "fan +" and "fan -" solder pads.
> The fan never comes on.  Checked the fan - its good.  Checked with Will,
> he told me the set point is 80 or 90 degrees C, and set in software and
> can't be changed.  I never get to 80 degrees C.
>
> I have one 2000A without the aux fan and one with.  The one with the aux
> fan that never runs, runs about 4 degrees C hotter than the one without.
> I attribute this to air flow blockage by the non-operating aux fan.
>
> Electronics reliability studies over the years all have pointed up the
> fact that cooler is better - the data is compelling.  A few degrees C
> however is not significant.  There may be hot spots within the amp that
> could benefit from more cooling - but the 2000A seems to be very
> reliable from all reports.
>
> The reason there is a 150 second warm-up period is because of the cold
> war - no pun intended.  The US blocked the export or thorium related
> technology to the USSR - judging it a strategic technology.  As a
> result, the Russians did not have thoriated tungsten filaments, and
> stuck instead with indirectly heated metal-oxide cathodes.  This is
> what's in the Svetlana 4CX800A.  Cathodes take time to heat up to a nice
> even dull-red temperature.  If you let the tube emit before the cathode
> is evenly warmed up, the hottest spots on the cathode will emit all the
> electrons (current), and you can burn a hole in the cathode at those
> spots.  The rest of the amp requires no warm-up, but the tubes need a
> good 150 seconds.  Tube life may be extended by holding off transmitting
> another 30-60 seconds after the timed warm-up, assuming you are not
> chasing the country you need to make the honor roll - in which case 150
> seconds seems like eternity.  The Alpha 99 timer is 180 seconds.
>
> _______________________________________________
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