[Amps] Cheap auxiliary amp cooling

[Jim Barber]

Yep, but really no different than my Henry 3KA running 200ma ZSAC @ 4KV 
with a pair of 3-500Z's. That one isn't good either. The tubes will glow 
orange after a minute or so just keyed with no drive.

73
Jim N7CXI

On 3/30/2012 8:41 AM, Carl wrote:
> 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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