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G5500 feedback pot fix



Hi gang;
Well, it is good to be back after a nightmare of pot problems with the
rotor system. Here is the problem; both 500 ohm feedback pots (AZ and el
at about $30.00 each) are open back----that is the resistive wire in them
is exposed to the atmosphere . Now in dry climates that may not be much
of a deal but here in south Texas, it is almost a  constant problem. My
pots both opened up after only about 1.5 years in service.. Cliff
Buttschardt, K7RR contacted me and kindly offered to do an autopsy on the
pots to determine the problem and he confirmed in both cases that the
resistive wire had corroded through. Here is how I hopefully corrected
that problem. I got some plastic prescription bottles and found a cap
that would fit snugly over the back of the pot. I wound the wire that
connects the wiper to the pot center connecting tab and fit that wire in
the pot opening, put the cap over the back of the pot and coated the
pot/cap interface with weather proof sealant. I took my wifes clear
fingernail polish and thoroughly coated the plastic/metal interfaces of
the pot body with it. While I had the rotors down, I changed all the
assembly anchoring bolts and nuts to stainless steel and put anti seize
in all the bolt sockets. As has been mentioned on previous posts some of
that original hardware was an absolute bear to get out but a buddy of
mine had a machine shop and was able to get the bolts out for me. I used
split stainless steel lock washers under all the new bolts. The ball
bearings showed some wear and corrosion so I replaced those in both
rotors. When it came time to reassemble the cases, I used weather
proofing sealant on all case mating surfaces except the entire bottom of
the elevation rotor as I wanted any accumulation of condensation to be
able to escape through the case weep hole and not to get trapped and pool
inside. Finally, I painted both rotor cases a dead white to help keep
temps down inside when the temps outside get so high as they do in south
Texas. There is a start/run capacitor in each rotor and maybe that white
exterior paint will keep them from drying out from the heat a little
longer. I "learned-by-doing" the calibration of the new pots to the
control box. In hindsight, its pretty easy to do------but then we all
know hindsight is 20/20.WWhile I was at it, I went to radioshack and
bought some hi-intensity LEDs to replace the pesky light bulbs in the
control box. 
That being said, I hope my rotor problems are over. I must say that in my
opinion it just doesn't seem right that as expensive as these units are ,
one should have these problems after < 2yrs of service---but I did and
here is how I tried to fix the shortcomings. If I can answer any
questions you might have on the above procedures/techniques please feel
free to contact me.

73 and see you on the birds

Bill, W5PGZ 

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