Potentiometer test
Connect tester (in ohmmeter mode) to plugs «4» And «5» servo connector and measure the total resistance of the potentiometer, which should be between 1.4-2.6 kΩ.
Connect the tester to the plugs «4» And «7» servo connector. Applying vacuum with a vacuum pump, slowly and completely push the pusher of the servo, while measuring the resistance: it should constantly decrease from 0.9-1.9 kOhm to 500 Ohm.
If the resistance value is not within the specified limits, replace the servo.