[TowerTalk] Follow up to Prosistel mechanical failure.

[William J. Nicosia]

                 Here's the outcome from my posting of last week 
regarding my Prosistel 2051d rotor that refused to rotate.
                 With the able assistance of John Crovelli, W2GD, we 
first confirmed that the motor was operable in situ. The rotor was then 
removed from its perch and brought to ground level. The motor housing 
was then removed and set aside. The DC motor was then carefully removed 
from the gear box housing and revealed that the coupling collar joining 
the motor drive shaft and the input shaft of the worm gear were held in 
place by a key and a tiny roll pin. Upon inspection the roll pin had 
been sheared and therefore the motor was free spinning. There was no 
indication as to why the pin had failed. A new pin was obtained at the 
local hardware emporium and pressed into place. We decided to reseal the 
motor housing to the gearbox by using matching Blue Permatex RTV. The 
rotor was then tested and re-calibrated in shack using the Green Heron 
RT-21 utility program to get the indicator pot in the 2051 into proper 
range. W2GD then replaced the unit in the tower, manually reset the 
antenna to North (including compensating for declination) and did a 
final test.
                 The upshot of this experience is that this rotor can 
fail but sustain no serious damage to the gear train due to a single 
roll pin, total cost for parts, 37 cents. My thanks to W2GD for his able 
work.

                 Bill Nicosia, W2ZKX (WB2ZKX)