[Amps] AL1200, RTTY contesting, temps, duty cycles (not 100%)

[Carl]

JI had nothing to do with that amp design.

Carl
KM1H

----- Original Message ----- 
From: "Kevin Normoyle" <knormoyle at surfnetusa.com>
Cc: <AMPS at contesting.com>
Sent: Saturday, July 04, 2009 11:51 PM
Subject: Re: [Amps] AL1200, RTTY contesting, temps, duty cycles (not 100%)


> Thanks Bill. I'll check that out.
> I would note that a higher speed blower  has already been done by people
> for the AL1200, and has been mentioned on this forum...i.e. I'm not
> inventing something.
>
> I wonder if the original blower Tom W8JI designed in, that was replaced
> out, was actually the higher speed blower.
>
> On 12/6/200, Tom W8IJ said the following (
> http://lists.contesting.com/archives//html/Amps/2000-12/msg00101.html )
>
> "The AL1200, because of complaints like yours, had the blower speed 
> reduced about 12 years ago. If you want to use the amp
> really HD, you need to speed the blower up a bit."
>
> "... Because people somehow expect you can move a room-full of air in a
> few minutes without making noise, the blower was sized as marginally as
> possible and still allow CW and SSB full duty operation. That places the
> blower too small for RTTY."
>
> "If you want to reduce noise, you can put sound deflectors over the
> outlet and inlet vents, as long as you maintain 1" of air space to the
> cabinet. A three sided box with the inlet facing down for the intake and
> reward for the exhaust works fine. That's what I use here but I also use
> the high-speed blower."
>
> Tom didn't provide the part number in his post, but I believe he's
> referring to same blower part number I referenced. (the G2E085-AA05-21).
> Note he didn't say he uses the high speed tap. He said "high speed
> blower". Which is the -21.
>
> When you look at the data sheets though, the -21 seems like less of a
> nice-to-have, and more of a gotta-have.
> I think this whole issue has been muddied by too much anecdotal info,
> with uncontrolled testing and duty cycles?
>
> Most people don't even have dummy load setups to test the configurations
> they will use in contests for even 30 minutes, so how can we be sure we
> have controlled data on anything?
>
> Are there not a lot of people using the higher speed blower?
> Here's another reference to the higher speed blower (search for the -21
> part # in the article.
> See Bill, I'm not really inventing/experimenting..it seems like trod 
> ground?
>
> I assumed people were already aware of this, since Tom obliquely
> referred to it.
>
> http://www.eham.net/forums/Amplifiers/12111
>
> My point is: that it seems like the AL-1200 has been hamstrung by this
> design change, and really needs the original blower. (the high speed one).
>
> -kevin
> ke6rad
>
>
> Bill, W6WRT wrote:
>> Kevin, I would strongly recommend not trying to finesse blower specs too
>> closely. There are too many variables and you could end up damaging the 
>> tube
>> with what appears to be adequate air flow.
>>
>> As the data sheet says, the only true measure of cooling effectiveness is 
>> the
>> temperature of the tube seals. I would suggest you get some 
>> color-changing paint
>> or crayon rated to change at 250 C and test the existing setup. You may 
>> find the
>> original blower is indeed adequate and you could save a bunch of time and
>> trouble.
>>
>> The paint and crayon are available from Mc-Master Carr. Go to
>> http://www.mcmaster.com/#temperature-indicating-paint/=2luo5g
>> and scroll down. Not expensive at all.
>>
>> 250C is 482F.
>>
>> 73, Bill W6WRT
>>
>>
>
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