[amsat-bb] Re: [Towertalk] Yaesu G-500A Rotor Question

[Jon Ogden]

on 11/14/02 10:49 PM, Roy Welch at rdwelch@swbell.net wrote:

> Disregard my previous message.  If the meter moves at all it won't be the
> meter terminal problem.  You may have a bad (open) rotor pot or
> intermittent cable lead, and it may only make connection at full rotation.
> You can easily check this with an ohm meter with the pot leads
> disconnected from the control box while moving the rotor through its range
> of movement.

I think this may be the problem.  I did some more testing.  I ripped the
rotor completely apart to get to the pot.  It appears that one end (say
terminal 1) of the pot has 7 Volts applied to it at all time.  The other end
(terminal 3) is connected to ground.  The wiper (terminal 2) is where the
voltage for the meter is taken off.  When I put the Ohm meter on the pot
between terminals 2 and 3, I can see the resistance change as I turn the
motor.  However, when going between terminals 1 and 2, the pot reads as an
open circuit.  There is no voltage drop across terminals 1 and 2 nor is
there any across 2 and 3.

Now I took and shorted terminals 1 and 2 together.  Then I was able to get
meter deflection but it's obviously not accurate.  But I know the meter
circuitry works.

Good thing I had to take it all apart though.  It looks like there is
supposed to be a gasket between the two halves of the rotor casting.  There
were just what looked like remains of a gasket on mine.  Guess I'll call
Yaesu in the morning and order some parts!

73,

Jon
NA9D