[Amps] Cheap auxiliary amp cooling

[Carl]

Isnt that exciting having to run almost 1100W idle with 2 tubes only rated 
at 1200W dissipation total?  No wonder they dont last long and availability 
is drying up.

Carl
KM1H


----- Original Message ----- 
From: "Jim Barber" <audioguy at q.com>
To: <Amps at contesting.com>
Sent: Friday, March 30, 2012 3:29 AM
Subject: [Amps] Cheap auxiliary amp cooling


> While playing with my new toy, (QRO HF2500DX) I found that I was able to
> confirm that it does indeed need auxiliary cooling for high duty cycle
> modes. Even at relatively low  or no power output - just the ZSAC is
> 450ma @ 2400V, or over 1000 watts of just plain old heat.
>
> I decided to check my computer parts supplier to see if there was
> anything that looked like it might work for a "booster" exhaust fan, and
> it turned out that a 250mm (10"!) 12V PC case fan has a brushless (no RF
> noise) DC motor, turns slow and makes little audible noise, but manages
> to move 105 CFM of air. (at zero back pressure, of course) They cost
> $26.99 USD in single units.
>
> I haven't built a sealed mount yet, but just sitting the fan on top of
> the case above the tubes dropped the exhaust temp 40-50F during
> 375/1500-watt AM transmissions. The noise of the "booster" fan is so low
> compared to the internal 50CFM blower that I can't really hear it.
> Legal-limit SSB conversations (with modest compression) get the
> airstream only lukewarm now, instead of 130F+ .
>
> I also bought a 243 CFM 8" 12VDC Conair-Rotron hurricane generator that
> I want to build a temperature-ramped PWM controller for when I get A
> Round Tuit. (probably 25khz, 30-100% duty cycle to copy the newer PC
> controllers, which work well) In the meantime, the cheap PC case fan
> seems to be getting the job done.
>
> 73,
> Jim N7CXI
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