unplugging the control cable should cause it to go to the counter
clockwise stop on the indicator. if it doesn't it probably means the
indicator drive motor is bad. this is a common problem with the yaesu g
series of rotors, i just had to fix one the other day again.
for a quick check to see if that is the problem do the following:
1. remove the metal cover (2 screws on sides and 4 feet)
2. remove front panel (3 screws on bottom, 2 on top)
3. pull front panel out about 1-2cm and look in to the gear
mechanism on the left side. you should see a small pulley with
a rubber belt on it.
4. plug in the rotor power but remove the control cable. be
careful, there are exposed connections where line power is available
but they are on the bottom side of the front panels on the other
side of the indicator at the switch.
5. turn on the rotor. with a small screw driver gently try to
turn the small pulley with the rubber belt, if it starts to slowly
turn the needle it confirms the motor is the problem. if it doesn't
start operating it could still be the motor, but may also be the
control board. if it goes back at full speed it might have been
a mechanical jam but i have never seen that here.
what happens is the commutator segments in the motor are too soft
so after a while the metal 'wipes' and powders enough to get in
between the commutator segments and essentially shorts out the
motor. if the controller is left on for long periods in this
condition it can also burn up the 2 current limiting resistors
and/or drive transistors on the little circuit board behind the
motor. giving the motor a push gets it past the shorted spot and
at least shows you that the rest of the drive and control stuff is
working, but it won't last.
a temporary fix goes as follows:
1. from the above condition, pull the power plug.
2. remove the small circuit board behind the drive motor (4 screws)
3. with needle nose pliers uncrimp the 3 crimps that hold the
plastic back onto the metal case of the motor.
4. very gently pry the plastic back off the motor.
5. with a needle or other very small type of dental pick tool
carefully scrape the gunk out from between the segments of the
commutator, you can remove the small nylon washer on top of the
shaft for better access.
6. use a paper clip or small pair of tweezers inserted through
the small slots on the plastic back to hold the commutator brushes
out of the way and carefully replace the plastic back.
7. recrimp the metal back. and replace the circuit board.
this should restore operation for a while, but eventually the
motor will need to be replaced. this process is much more
involved as you have to disassemble basically the whole front
panel to get to it.
Graham Dacombe wrote:
>
> Greeting all,
>
> Having lowered my 50ft tower to do some antenna maintenance I thought I
> should re grease the Rotor at the same time, to the best of my knowledge I
> put it back together as I took it apart ???
>
> On another tower with the same Rotor when I unplug the control cable from
> the rear of the controller the needle immediately returns to the zero
> degrees point, plug it in again and it returns to wherever the rotor was
> last stopped.
>
> For some unknown reason this controller has got itself permanently in the
> extreme clockwise direction ( 120 degrees overlap) and does not move back
> to Zero degrees.
>
> I have used my second controller to set the rotor itself to it's correct
> position 75 degrees while the tower is down (tower hinges from ground
> level, so the 40 meter beam has it's reflector flat down on the lawn with
> the beam pointing skywards.
>
> Can anyone tell me how, with the controller cable disconnected to get the
> controller back a complete revolution plus to 75 degrees or how to make it
> return to the zero point, is it possible to somehow short out the correct
> two points in the socket on the back and make it travel back anticlockwise?
> as operating any of the front controls fail to achieve this.
>
> Regards Graham, ZL3NZ at Waikuku Beach,
> 30 Kilometers North of Christchurch, New Zealand.
>
> --
> FAQ on WWW: http://www.contesting.com/towertalkfaq.html
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--
David Robbins K1TTT (ex KY1H)
k1ttt@berkshire.net or robbins@berkshire.net
http://www.berkshire.net/~robbins/k1ttt.html
--
FAQ on WWW: http://www.contesting.com/towertalkfaq.html
Submissions: towertalk@contesting.com
Administrative requests: towertalk-REQUEST@contesting.com
Problems: owner-towertalk@contesting.com
Search: http://www.contesting.com/km9p/search.htm
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