To set the electrical offset of the tilt servo to 0V by adjusting the inclination of the tilt sensor.
Symptoms when incorrectly adjusted
Note: This is a major mechanical adjustment to the player – it is suggested that you do not perform this adjustment unless other calibration procedures are not possible due to misalignment!
Note: The original service manual states that the player should be in normal mode with the tilt servo turned off however this is not actually possible to do (the tilt mode control is only available in service mode). As the service manual instructions are not possible to perform, the following method is the author’s suggested technique (please see the original service manual for the manufacturer’s recommended instructions).
Note: This adjustment is greatly affected by ambient light. Ensure that the adjustment is made with no lights over the player and with the ambient light as dim as possible. You can also place a LaserDisc album cover over the top of the player when checking the measurement (to block stray light).
Note: This adjustment must be performed with the player placed horizontally with a frame in the range of 2,000 to 10,000 to ensure the sensor output is not influenced by the mirrored surface on the inner-edge of the disc or external light at the outer-edge.
Connect the oscilloscope to TP1-8 (Tilt error). Use the following oscilloscope settings:
Channel 1: Probe x10, 50mV and X-axis in 1 second roll mode (if the oscilloscope is faster than 20MHz turn on the bandwidth limiter for the channel).
Put the player in the following condition:
- Service mode
- Tracking loop open
- Tilt servo – disconnect CN4
Place the player in service mode and skip to around frame 5,000. Engage the plunger. Adjust the tilt sensor inclination screw in small increments until the DC RMS of the measured signal is +-20mV around ground.
A clockwise adjustment raises the tilt error value and an anti-clockwise adjustment lowers it. The correct position of a screwdriver for the adjustment is shown in the following photograph:
The actual adjustment screw is almost impossible to see without removing the optical assembly from the LaserDisc player. The following picture shows the adjustment screw more clearly:
Once adjustment is complete set the tilt servo to on (reconnect CN4) and search for frame 115 (in normal mode). Verify that crosstalk on both sides of the picture is both minimal and symmetrical.