[Amps] Cheap auxiliary amp cooling

[Carl]

That sounds like a shorted zener and running at zero bias or just poor 
engineering but you cant blame the tubes. Mine run at 120ma at 3000V in the 
LK-500ZC and IMD 3 is in the low -40's.

Carl
KM1H


----- Original Message ----- 
From: "Jim Barber" <audioguy at q.com>
Cc: <Amps at contesting.com>
Sent: Friday, March 30, 2012 1:21 PM
Subject: Re: [Amps] Cheap auxiliary amp cooling


>
> 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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>>> Amps at contesting.com
>>> http://lists.contesting.com/mailman/listinfo/amps
>>>
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>>
>>
>
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