Adjusts the inclination of the slider shaft so that the pick-up assembly moves parallel the disc. The first adjustment is to bring the centre-point correct.
The second adjustment ensures the the mechanical height setting of the drive shaft is as level as possible across the whole span of the disc and ensures that the player can compensate the drive shaft height using the tilt mechanism when necessary (as the disc tends to ‘droop’ towards the outer edge due to the weight of the disc itself).
Symptoms when incorrectly adjusted
Lens comes contact with the disc surface. Warped discs cannot be played.
Adjustment procedure (Pick-up assembly height adjustment)
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! This adjustment should be ‘fixed’ by the factory and should not require adjustment.
Note: This adjustment must be performed with the player placed horizontally.
Connect the oscilloscope to TP1-3 (Focus return). Use the following oscilloscope settings:
Channel 1: Probe x10, 20mV and 5ms/div (if the oscilloscope is faster than 20MHz turn on the bandwidth limiter for the channel).
Put the player in the following condition:
- Service mode
- Play mode
- Tracking servo loop open
- Tilt servo 10:off
Play the test disc from service mode by pressing the play button – Power up the player whilst holding the DISPLAY key to put the player in diagnosis mode. Press play either on the remote or the player’s front-panel (note: this also opens the tracking servo loop). Skip to around frame #10,000 (the approximate centre of the laserdisc) – In diagnosis mode you can press CHP/TIM on the remote to place the player in frame mode, then enter 10,000 (the frame number) using the numeric keys followed by [SEARCH] – the player will attempt to move to the requested frame. If it’s not possible to skip to frame 10,000 and play the disc it may be necessary to repeat the “Grating temporary adjustment and tracking balance adjustment” (especially the tracking balance adjustment).
Lock the pick-up in place by pressing the plunger release button on the service remote ([POWER] on the RMC remote) – this will engage the pick-up lock (you may need to move the pick-up slightly by hand to make sure the lock is fully engaged).
Measure the voltage at TP1-3 (via the RC filter) using the oscilloscope. The focus return voltage should be 0V +- 10mV with respect to ground. If the focus return voltage is higher or lower than required, the pick-up height adjustment screw will need to be adjusted using a 2mm hex wrench. When adjusting the screw the pressure from the hex wrench will cause the voltage level to shift; make sure you are not applying pressure to the adjustment screw when measuring.
The pick-up height adjustment screw is accessible through the FTSB module (when the player is tracking around frame 10,000), as shown in the following photograph:
Move the screw slowly in either direction observing the focus return voltage. Set the screw in the optimum position to ensure the focus return voltage is as close to 0V as possible, as shown in the following oscilloscope trace:
Once the measurement is in correct unlock the pick-up by pressing the plunger pull button ([PAUSE] on the RMC).
Adjustment procedure (Drive shaft levelness adjustment)
Note: This adjustment must be performed with the player placed horizontally
Move to frame 115 and measure the TP1-3 voltage. Use the tilt up and tilt down controls to adjust the tilt of the optical assembly until the voltage is as close to 0V as possible (user [CHAPTER SKIP FWD] to move the tilt servo up and [CHAPTER SKIP REV] to move it down on the RMC). Make a note of the lowest measurement and label this as ‘V1’.
Repeat the same procedure at frame 10,000, make a note of the lowest measurement and label this as ‘V2’.
Repeat the same procedure at frame 22,000, make a note of the lowest measurement and label this as ‘V3’
V1 – V2 should be 20mV or less. V3 – V2 should be 20mVs or less. If either measurement is incorrect repeat the pick-up assembly height adjustment and measure again.