Paint the inside and outside black. The black inside will absorb the heat
more effectively and the black outside will radiate it more effectively.
Bob
K8MLM
In a message dated 12/18/2010 1:45:29 P.M. Eastern Standard Time,
rex@lint.mv.com writes:
So what's the groups take on Measure's "paint it black"? Debunked or
still
a valid argument?
http://www.somis.org/SB220ci.html
-Rex-
Rex Lint, Consultant
26 Brek Drive
Merrimack, NH 03054
PH: 603-860-7651
-----Original Message-----
From: amps-bounces@contesting.com [mailto:amps-bounces@contesting.com] On
Behalf Of Mike
Sent: Saturday, December 18, 2010 12:45 PM
To: amps@contesting.com
Subject: Re: [Amps] Fan for SB220
If the equipment has strong forced-air cooling, then heat-sink surface
finish isn't very important. If anodized with black oxide coating it will
reduce thermal resistance up to 25% if convection cooling.
We did these test in our development lab years ago to prove a point to
marketing who wanted a silver look because it was "Prettier".
Mike
If the equipment has low airflow, then radiation cooling becomes important,
and black anodized aluminum radiates enormously better than bare unfinished
aluminum.
-----Original Message-----
From: amps-bounces@contesting.com [mailto:amps-bounces@contesting.com] On
Behalf Of Gary Smith
Sent: Saturday, December 18, 2010 9:12 AM
To: Carl; amps@contesting.com
Subject: Re: [Amps] Fan for SB220
This may seem to be to at first but let me go on.
Years ago the same belief existed regarding black vs. sliver on the
cylinders of cast iron Harley -Davison motorcycles. (Yes, I am that old I
have seen (and owned H-D's) with cast iron cylinders.) One school of
thought
was "paint`em black, it'll draw the heat out rather than keep it in" The
other group's belief was "paint it silver, that will draw the heat out" and
so forth. The comeuppance was that H-D offered bother colors of paint in
touch up cans when the cylinders got dinged to appease both groups
Pont here is make an aluminum separator and paint it black? Or just leave
it plain finish. Me thinks the difference in temp would not be worth the
effort, Its just a matter of belief.
But as a director of air one way or the other, that's a different subject.
Gary...wa6fgi
----- Original Message -----
From: Carl
To: donroden@hiwaay.net ; amps@contesting.com
Sent: Friday, December 17, 2010 6:33 PM
Subject: Re: [Amps] Fan for SB220
I dont see how that shield helps anything Don, especially black. Have you
done any temperature tests on the tubes and shield? A shroud partially or
fully encloses the fan as in automotive use.
Carl
KM1H
----- Original Message -----
From: <donroden@hiwaay.net>
To: <amps@contesting.com>
Sent: Friday, December 17, 2010 10:36 AM
Subject: Re: [Amps] Fan for SB220
>
> Carl,
>
> I'm supprised no one has mentioned adding a black aluminum shield
> between two 3-500s to help prevent the two tubes from radiating heat (
> and rf ) into each other. I've done this on my SB220, but didn't do
> any IMD measurements. It seems to improve the air flow too.
>
> Don R W4DNR
>
> Quoting Carl <km1h@jeremy.mv.com>:
>
>> Tests have shown that the turbulance from the high speed Harbach does
>> little
>> for the cooling unless a shroud is added. The one saving grace is a WW
>> resistor can be added to reduce the speed a bit and reduce the noise;
>> 150-250 Ohms 20W seems to do well. Dentron and Amp Supply used a
resistor
>> in
>> many of their amps.
>>
>> Carl
>> KM1H
>>
>>
>> ----- Original Message -----
>> From: "David G4FTC" <g4ftc@hotmail.com>
>> To: <amps@contesting.com>
>> Sent: Friday, December 17, 2010 1:47 AM
>> Subject: Re: [Amps] Fan for SB220
>>
>>
>>>
>>>
>>>> A local ham buddy just got back into the hobby after an 8 year hiatus
>>>> and
>>>> got a hold of 2 SB220's. He noticed they run hot and he asked the
>>>> following question...so I figured there are folks out here who might
>>>> know
>>>> the answer
>>>>
>>>> "....see how guys like the Harbach fan kit for the SB220? Mine is
>>>> running
>>>> hot and LOUD. I oiled the
>>>> bearings and cleaned it off of dust, but it's still got to go"
>>>>
>>>> Anyone done this mod?
>>>>
>>>> I recommended a small muffin on top to help extract the hot air for
>>>> now.
>>>> I did it on my old 30L1 and it sure cooled it down.
>>>>
>>>> Thanks
>>>
>>>
>>>
>>> I'm using one of the Harbach fans on a SB220 - they move a lot more
air
>>> than the original Heathkit fans.
>>>
>>> Higher air-flow = higher noise
>>>
>>> But I can't say I've noticed that it runs hot.
>>>
>>> Regards
>>>
>>> David G4FTC
>>>
>>>
>>> _______________________________________________
>>> Amps mailing list
>>> Amps@contesting.com
>>> http://lists.contesting.com/mailman/listinfo/amps
>>
>> _______________________________________________
>> Amps mailing list
>> Amps@contesting.com
>> http://lists.contesting.com/mailman/listinfo/amps
>>
>
>
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