----- Original Message ----- From: "Jeff Griffin" kb2m@comcast.net To: amsat-bb@amsat.org Sent: Tuesday, August 14, 2007 4:24 PM Subject: [amsat-bb] Yaesu 5500 rotor problem

Well I finally recovered enough from my shoulder operation to take down

my

5500 rotor. I took it apart and the three wires going to the pot seem ok, bummer. I also checked the cables as best I could and they seem ok. Is it possible the azimuth rotor indicater pot is bad? If so how do I check it?

73 Jeff kb2m

Hi Jeff, KB2M

If you like to independently test the azimuth potentiometer alone and see if it is bad or not disconnect from the motor the three wires going from the control box to terminals A1-A2 and A3 of the motor

Connecting an ohmmeter across terminals A1 and A3 of the motor you should read about 500 ohm

Now connect your ohmmeter between terminals A2 and A3 of the motor.

Manually rotating the motor fully CCW up to limit switch you must see the resistance of the pot slowly to decrease up to 0 ohm and rotating the motor fully CW up to limit switch you must see the resistance slowly to increase from 0 ohm to about 500 ohm

Now connect your ohmmeter between terminals A2 and A1 of the motor.

Manually rotating the motor fully CCW up to limit switch you must see the resistance of the pot slowly to increase up to 500 ohm and rotating the motor fully CW up to limit switch you must see the resistance slowly to decrease from 500 ohm to 0 ohm

Sometime the shaft of the pot mounted inside the rotator becames loose with its fixing small screw in to the gear box.

To test if this condition do exists or not rotate the motor angularly midway from the CW and CCW limit switches (usually to North).

Connecting an ohmmeter between terminals A2 and A3 and then to terminals A2 and A1 of the motor you should read about the same pot resistance of 250 ohm indicating that the pot setting inside the rotator is well balanced.

A better procedure to test the pot and part of the associated circuitry is the following one:

Without disconnecting any wire from the back of your control box connect a DC voltmeter between terminals A1 and A3 and you should read about 5.5 volt DC

Connect the DC voltmeter between terminals A2 and A3

When the antenna is rotated fully CCW you should read 0 volt and rotating the antenna by 360° CW the voltage should linearly increase up to about 5.5 volt

If you pass the above test than the 500 ohm potentiometer inside the rotator is OK

If not it means that or the potentiometer is gone or one of the wires A1-A2-A3 running from the control box to the antenna is interrupded.

If the potentiometer test is passed than the problem shoud be located in the wires connecting the control box to the motor or inside the control box itself.

To test if the control box alone is OK or not disconnect wires A1-A2-A3 from the rear of control box and connect to it a 500 ohm wire wound potentiometer to simulate the potentiometer inside the rotator.

Please note that the wiper of the potentiometer must be connected to A2 of the control box.

Manually turning the above potentiometer you should have the angular position indication of the pot wiper (A2 wire) both on control box analog meter and PC software.

I hope this helps

73" de

i8CVS Domenico