[amsat-bb] Yaesu G-5500 Potentiometer replacement

Todd superiortrading at gci.net
Thu Mar 12 18:14:18 UTC 2015

I recently bought a _very slightly_ (like new) used Yaesu G-5500 rotator 
and have had some issues with the indication system. During rotation of 
the elevation rotor sometimes both indication meters would sometimes 
fluctuate violently to full scale. Finally the elevation indicator just 
stopped at 90 degrees and stayed there or went to zero when hitting the 
zero stop microswitch.  Anyway, if figured the position potentiometer 
was the problem and opened up the unit and _found the gear on the pot 
shaft was slipping due to the set screw not holding_. Although, it would 
grab at some point during the rotation cycle again and hence be out of 
sync now with the motor stop! This grabbing again in the rotation cycle 
destroyed the pot. Got two (one spare) replacement pots from Yaesu and 
installed and calibrated very carefully I might add. Adjusted pot to 
display "0" degrees, installed gear on pot shaft and rechecked 
indication to be be sure I still read "0". Assembled motor gearing with 
boom tube so stop switch @ zero  just actuated. Installed other case 
half and checked ok and dead on after standard manual cal.
Anyway, just checked the azimuth operation and see that the indication 
is off at 90 degrees by 10 degrees or so. Watching needle from zero the 
needle delays in movement by a couple of seconds after motor starts 
turning. I suspect another set screw slipping again. I will investigate 
further. I'm getting closer to interfacing the LVB Tracker now. Anyhow, 
after looking everywhere on this BB and internet for any procedure to 
change these pots in either rotator I did find this posting from a Yaesu 
Rep that gives a guide to a individual if he decides to take on the task 
of changing out the azimuth pot. The Rep advises him to sent the unit to 
him in California.


  *   The grease that our technician uses to grease the bearings is
    Valvoline DuraBlend Synthetic Part# VV278.

  *   In regards to replacing the pot, we strongly recommend that you
    send the rotor to us to have the pot replaced. We make this
    recommendation based on past experiences when users have tried to
    replace the pot but *_did not properly align and position the pot
    during replacement and re-assembly._* If not aligned and
    re-assembled properly, damage to the rotor can occur. That being
    said below are some points to keep in mind should you decide to do
    the replacement yourself.

 1. To orient pot shaft, place multimeter probes on Pin 1(Brown) & Pin
    2(Yellow).  Turn pot shaft until resistance reads 250+- Ω

 2. Reinstall gears on the pot and recheck resistance as described above.

 3. With Rotator top off connect control cable to the rotator and
    control box.

 4. Set multimeter to VDC and insert probes into Pin 2 and 3 of Control
    Box jack.

 5. Using the CCW switch rotate until VDC match the following:


             G-800, 1000, 2800DXA, G-5500 AZIMUTH=0.540vdc

             G-800, 1000, 2800SA=0.180vdc

 6. With the rotator connector facing you, position the Rotation Limiter
    arm to the right until it just touches the right stop. FAILURE TO DO

 7. Install the rotator top with the raised alignment mark on the top
    half of rotator case matching the raised alignment mark on the
    bottom half of the rotator case.

 8. Recalibrate the rotator and control box according to the instruction
    found in your Operating Manual.

             Best regards,
             Technical Support Supervisor

This is the kind of information owners of these rotators need to 
properly service and maintain these units. Hope this information can 
help anyone with changing out these potentiometers.

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