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Re: [Amps] Current draw fan Alpha 77

Subject: Re: [Amps] Current draw fan Alpha 77
From: "Gary Smith" <>
Date: Tue, 24 Oct 2017 13:45:19 -0400
List-post: <>
Hi Martin,

They made several of the 77 line and I 
should have been more specific, this is a 
two tube variety. I'm not sure if it came 
originally with two or a 2nd was added 
along the way. It's an amp with a lot of 
overhead available to me as I leave it in 
the CW/Low Volt mode and it loafs along at 
legal limits regardless of what contest 
I'm in.

The blower is just plain loud and it is 
set at full speed by the setting on the 
adjustable wire wound resistor, it came 
that way and I haven't lowered the speed. 
It's running right now and moving curtains 
10 feet away & that doesn't make sense if 
I don't need the CFM. I don't see a 
thermostat or probe located anywhere 
(except for the Sunbeam oven thermometer 
probe I have in the back to keep track of 
the exhaust temp), it ranges from 91F at 
idle to between 130-150F, tops.

I just bought a thermostat & probe with a 
10 amp relay which I'm going to utilize. 
I'll have to figure out which way will 
allow me to have the fan run at a slow 
speed & run a connection to the other end 
of the adjustable enamel wire-wound 
resistor, to the relay. When it reaches 
the target temp (I'm guessing 110F should 
be a good point to engage full speed), 
it'll run the fan at maximum till it cools 
down and defaults back to slow.

Noisy bearings are a bugger and I don't 
hear that kind of sound, it's just a loud 
blower running at maximum. I rarely 
transmit any more, I listen more so a 
slower speed & less noise just makes 
sense. I did just recently post my 
cleaning the squirrel cage when I first 
bought it, and how that made a marked 
difference in the turbulence & sound. That 
was 6-7 years ago and I'm going to do it 
again while I have the top off, just to be 

I remember the cage had a very small 
amount of surface rust which I removed, 
that roughness added to the turbulence. If 
I see any has returned maybe it would help 
if I made it spray painted the cage with 
enamel to increase the laminar flow & make 
it a snap to clean again, easy to do and 
wouldn't hurt anything.

I'll let you know how the thermostat works 

Thanks for the reply & 73,


> Hello Gary,
> My 77D(x) has a rheostat in the blower supply. I'm not sure if that
> was the same for all. Since mine is an early model it also has a
> thermostat switch mounted on the exhaust plenum that shorts out this
> resistor. I believe that was later deleted. I have the blower set
> quiet slow with the rheostat but the air out the back never seems to
> get too hot and the thermostat has never switched to high speed but
> then I don't tend to use it for high duty cycle modes.
> My blower is quite noisy, definitely worn bearings and I plan to
> replace them in the next few weeks. If that proves successful maybe I
> can run the blower a bit harder without needing ear defenders.
> Whilst some might argue the original 77 transformer was a bit weedy
> and the tank circuit somewhat undersized in some situations (2 tubes
> on 160m) the blower by comparison seems almost excessive in the 77,
> almost able to achieve that desired state of being able to lift the
> tube from its socket :) This on a 50Hz supply where a lot of blowers
> are distinctly under sized.
> 73, Martin, HS0ZED
> On 23/10/2017 18:35, Gary Smith wrote:
> > Not sure why my message didn't send
> > properly but I'd sent:
> >
> > Got it. Thanks for the direct replies.
> >
> >
> > I am finally getting around to adding a
> > thermostat to the amp to allow slower fan
> > rotation at idle and full rotation when
> > transmitting. The blower on this thing is
> > a beast.
> >
> >
> > 73,
> >
> >
> > Gary
> > KA1J
> > _______________________________________________
> > Amps mailing list
> >
> >
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