[amsat-bb] Re: Kenpro elevation rotor repair

Roy rdwelch at swbell.net
Sat Sep 27 13:46:43 PDT 2008

Hi Guys,

My two cents worth.  It looks like Sebastian has made all of the 
checks.  I assume the rotor will not move in either direction.  It's 
possible that something had fallen into the gear train, jamming the 
works but it does sound more like a bad motor.  Have you measured all of 
the voltages and especially the resistance values on the motor leads as 
shown in the owner's manual?  If the resistances all look good and the 
supply voltages are good then I would check the resistance from each 
motor lead to the metal case to see if there is a short circuit to the 
rotor housing.  I'm not sure but in some countries RFI hash protection 
has been added to the rotor circuitry consisting of small RF chokes and 
capacitors mounted inside the rotor case.  For example, my Emoto rotors 
don't have it but the versions sold in some European countries do have 
it.  You might check to see if there is a similar thing in your rotor 
and that there are no failures there.  I doubt that this is the problem 
however.  Good luck.

Roy -- W0SL

Sangat Singh wrote:
> Sebastian,
> I had a similar problem. In my case I found that the 24 volt motor had 
> packed up.  Since I had another Elevation Rotator with the faulty pot 
> sitting on my bench for half a century,  I swapped the motor and it 
> worked.  The motor is easily removed.  Please remove the 4 screws that 
> hold the motor and then try powering up and see if the motor works.  I 
> suppose you won't have a spare motor. I am trying to get the faulty 
> motor rewired.  Our local talent can do wonderful things. 
> You might consult Roy Welch who has a great knowledge on ailing Yaesu 
> rotators.  I am sure he has seen this mail and may have some valuable 
> suggestions.  Do share your experience if you manage to fix this problem.
> Opening nuts is a big problem and your Motor Cycle workshop should be 
> able to help.  I got mine too opened that way.
> 73
> Sangat, 9M2SS 
> 2008/9/27 Sebastian <w4as at bellsouth.net <mailto:w4as at bellsouth.net>>
>     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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>     expressed are those of the author.
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> -- 
> Sangat Singh
> 53, Jln. Perdana
> National Planetarium
> 50480 Kuala Lumpur (MALAYSIA)
> Mobile: +60122838873
> Office: +60322787388
> FAX: +60322738873
> Skype ID: sukhija


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