torsdag den 22. juni 2017

Repairing my Kenpro KR-550 elevation rotor

My Kenpro KR-550 rotator was "frozen" and could not move in any direction. I searched for advice (Google is your friend) and found instructions from PA1IVO on how to disassemble and repair the rotor.

Disassembly of the rotor cabinet was tricky! The 8 bolts holding the cabinet together were completely stuck. I had to apply a dismounting technique, which I learned from a Youtube video: Heat the bolt and apply candle vax to the thread. That surprisingly worked!

The bolt can be loosened after treating it with candle vax.
Next step was to spot the error. The motor and gearbox were in good condition, and they operated normally when power was applied. However, the big gear wheel, which is fitted on the boom shaft, had chunks of clotted grease between the teeth. This was the core problem, and it prevented the big gear wheel from rotating. I removed the chunks and cleaned all gear wheels.

Clotted grease was found in the gear wheel.

Finally, I replaced the 500 ohm potentiometer inside the rotor. The new potentiometer was purchased at UKW-Berichte in their webshop (item 01999-KR-Poti). The spare-part cost me 27 EUR plus shipping from Germany to Denmark.  

The new 500 ohm potentiometer.
Now it was time to assemble the rotor. The gasket between the two halves of the cabinet was renewed. I applied Loctite 243 to the 8 cabinet bolts. Loctite 243 prevents loosening due to vibration, and it permits disassembly with hand tools for servicing.

The elevation rotor is now back in operation. I am eager to resume my EME project, and I will report my progress here.

73 from OZ1BXM Lars

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