[amsat-bb] Kenpro elevation rotor repair

Sebastian w4as at bellsouth.net
Sat Sep 27 08:01:43 PDT 2008

Well I had been back on the birds for the last 3 months or so, and  
while I was getting ready for an AO-16 pass a few days ago, my  
elevation rotor on my Yaesu G-5400B stopped at about 10 degrees.

That's it.  It won't go back down or up.

So I checked the wiring on the rotor, everything appeared fine.  I  
removed the elevation rotor from the azimuthal, and took it inside.  I  
made a small patch cord to go from the control box to the rotor, but  
no luck.  All I get is the display of the elevation of about 10  
degrees, and I hear a little hum when I attempt to move it up or  
down.  This tells me that the potentiometer is probably good, and the  
motor is receiving power.

I've removed the small nameplate on the side, and there is no water  
inside, and I can see the ball bears; there doesn't appear to be any  
rust inside.  I also removed the terminal assembly in case one of the  
wire had come loose, or had a cold solder joint, but I didn't find any  
problems there.  Looking at the diagram of the rotor, there appears to  
only be a small 24 volt motor which turns this; along with numerous  
mechanical parts.

So the question is.  Before I send this to Yaesu, has anyone had this  
problem before, is it a minor one (something that I could fix myself),  
or is best left to Yaesu?  Before anyone mentions, Norm's no longer  
services these rotors.  The four 'screws' that hold the two parts are  
impossible for me to loosen.  I would have to use a vice, but I do  
have a friend with a motorcycle repair business who I'm sure could  
open it for me in 60 seconds.  To me, this looks like a jigsaw puzzle  
by looking at the diagram.

The rotor was in service for about a couple of years back in the early  
90s.  It then sat inside without any use, up until a few months ago.   
If the consensus is to send it to Yaesu, should I bother to send in  
the azimuthal rotor, or should I follow the "don't fix it if it aint  
broken" rule?

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