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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