I know that the reed switch in the OR2800 can fail due to EMP from close by
lightning strikes. I have also read where people report intermittent issues
with the reed switch.
I also seem to have an intermittent problem with the reed switch in my
OR2800DC. However, my problem seems to track with temperature, indicating to
that it may not be the switch itself but potentially a flakey connection or an
intermittent short either in the rotor itself or at the cable splice (I have
older version with the round connector on the pigtail and not the breakout box).
In my case, when the ambient temperature is low (below about 45F), everything
fine and the rotor works exactly as expected - no problems tracking rotation,
pointing accuracy issues, or position repeatability issues. However, once the
temperature goes above about 50 F, the switch reads closed all the time. I
verified that it is closing at the higher temperature as during the last
episode, when I went QRT the switch was open - two hours later when I went back
on the air it was closed and would not toggle when I attempted to turn the
rotor. Also, when I force the rotor to turn in the RT21 debug mode, I see
NO change in contact resistance, which means that if the reed is shorted, it's
Then, the next morning when it's cold again, the switch is open and the rotor
works normally. I have seen this happen consistently for the last two weeks.
I suspect that this is NOT the reed itself, but potentially one of
1) Internal short on the leads to the switch, possibly due to insulation
failure on wires that are wire tied to torque plate from years of temperature
2) Internal short at the splice going into round connector on pigtail.
3) Clearance between the head of the switch and the gear that contains the
activating magnet. As the temperature rises the clearance may get smaller
leading to permanent activation of the switch. I think this is very
unlikely unless the fastener that is holding the switch to the torque plate has
come loose. As well, I would expect at least SOME fluctuation in resistance as
the magnet moves.
Question: Has anyone else encountered the above symptoms (intermittent
failure that tracks temperature). If so, what was the actual root cause in
Jeffrey K. Okamitsu, PhD, MBA
TowerTalk mailing list