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
sure.
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
out.
Thanks for the reply & 73,
Gary
KA1J
> 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
> > Amps@contesting.com
> > http://lists.contesting.com/mailman/listinfo/amps
>
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