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Re: G-5400B Elevation Rotor, Part II



Bill and Jerry, et al:

I'VE BEEN HERE BEFORE.  Sorry I missed your original post and didn't
respond sooner. . .

Have learned a LOT about the G5400s over the last 5+ years of fully
automated operation.  There are some serious design issues; I'll try to
SUMMARIZE my experiences and lessons learned/corrective actions.

First failure:  I hadn't done as well at counter balancing the load as I
thought, think I overtorqued the elevation rotor and it failed, taking
the power transformer with it.  THen the fuse blew.

Fixed my error, learned that you can easily get the wrong elevation
motor (there were two styles, look closely at the number ON THE MOTOR,
which is probably same as on the INSERT to the manual -- not the
original page.)  Learned that there is NO overload/overheat protection
in the elevation motor. Limit stops only prevent going into the stops,
nothing else.  Poor design, in my opinion.  Protected the transformer by
going to a progressively smaller slow blow fuse, to allow starting
current, but lower allowed long-term current.  Have had no more
transformer failures.

Had an azimuth sensor go "flakey", opened up the azimuth rotor to
replace, and learned that the overload temperature sensor for the
azimuth motor is held on by cheap cellophane tape, which had dried out. 
Consequently, the sensor was measuring air temperature, not motor temp. 
Fixed that with good tape backed up by a UV resistant tie-wrap, which I
had handy.

Lost another elevation motor when the shaft spun in the plastic gear,
melting the gear and driving it off to the point of ineffectiveness. 
(motor still good, now a spare, if I can ever get the clutch apart).

Lost another elevation motor (shorted winding due to overheat) when a
tree grew into the path of the antenna at a certain az/el combination. 
Tree branch 1, rotor 0.  Fuse protected all other circuitry, replaced
motor.  Chain saw 1, tree branch -- history.

Rewrote my automatic tracking software to much more aggressively detect
attempt to move followed by no motion and shut down until operator
intervention.

Hope all this experience helps.

73,
Jim
wb4gcs@amsat.org


Bill wrote:
> 
> K5OE@aol.com wrote:
> 
> > Thanks to all who offered advice and help on my blown transformer.  I was
> > able to source a replacement and have it installed.  The azimuth works fine
> > now, but the elevation appears dead.
> >
> > It is at zero degrees right now.  When UP is selected, the 26 Vac makes it to
> > the rotor terminals, but nothing happens.  When the DN is selected, I can
> > feel the motor "hum" even though it is apparently at the DN limit switch
> > stop.  The schematic shows the UP limit switch as the only thing in the
> > circuit other than the motor, and since it seems to "hum" with the DN
> > pressed, I am suspicious the UP limit switch is somehow is stuck open.
> > Anyone see this before?  Any ideas?   5 hours to AO-40 AOS here!
> > 73,
> > Jerry, K5OE
> > ----
> > Via the amsat-bb mailing list at AMSAT.ORG courtesy of AMSAT-NA.
> > To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org
> 
> Hi Jerry:
> 
> Sounds familiar.....Several hyears ago, the 100mfd electrolytic lost capacity and
> had that sort of sympton.  The 5600 has the capacitors in the rotors, the 5400
> has one in the display unit nil in the rotors..  FWIW.  Good .luck...and the
> capacitors are available at your nearest appliance dealer.
> 
> ----
> Via the amsat-bb mailing list at AMSAT.ORG courtesy of AMSAT-NA.
> To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org

----
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