[Bob Cook]

Paul

re autopilot. I meant that the DG heading bug should determine the direction the autopilot steers the AC.

I found the manual. You have either a follower potentiometer in the actuator that failed or the transistor (s) that have quit.

Just remove the four fillister head screws. The electronics can be removed without removing the motor and clutch assembly. You can still fly the aircraft but placard the autopilot and disconnect fuse or breaker.

While you are at it you should check and clean brushes in the motor.

The transistors are
Q1,2 2n1040
Q3,4,5,5,6,7,8 2n1546
CR1 1n2972
CR2 1n2970

left turn is Q1,3,5,7
right turn is Q2,4,6,8

What is tricky is all the above transistors are DC coupled and constitute a DC amplifier.

One of the transistors /2n1546 most likely / is likely shorted and needs to be replaced. A local radio shop or ham can test the transistors and replace the defective unit.

Check the potentiometer with an ohm meter and make sure it is okay if transistors check out okay. The pot provides positional information to the autopilot computer to electrically show the deflection of the aileron. If the pot is open the autopilot thinks the aileron is where it isn't <G>.

pin out of plug (small round one) is
A = voltage CCW
B = voltage CW
E = DC return
C = 10 VDC(-) reference volt when ap is on.
J,H +24 vDC
k Follower on potentiometer
D effort (motor winding)
F effort (motor winding)
Ground = aircraft.

The removable portion is a PC board with heatsinks. Rotate collar on connector and pull gently. The connector is polarized.
It is a small round blue body that supplies connections to the controller.

I can scan schematics etc. but almost guarantee this is the problem.

This is a PA-510A Actuator. there are different transistors based on a 12 or 24 v actuator! Do not get these mixed up.

If this is okay then check to voltages in the connector / -10 / +24 to make sure they are present. The 24 volt is for sure based on the motor running. The -10 ref voltage if not present could cause similiar problem by biasing the amplifier in one direction.

The elevator servo in the port tailboom is exactly the same and if you wanted to do a quick test you can substitute the electronic portion above (swap out). Your choice.

In the end, you should be able to pull out the turn know and move the ailerons left or right on the ground with the AP engaged as a test for the servos.

fyi

Bob