To set the object lens to its optimum position so that it works optimally with the focus servo while playing a disc.
Symptoms when incorrectly adjusted
Symptoms when incorrectly adjusted: Crosstalk.
Connect the oscilloscope to TP1-9 (TRKG ERROR). Use the following oscilloscope settings:
Channel 1: Probe x10, 100mV 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
- Focus balance ‘0’
Play the test disc in service mode. Around frame 1,000 open the tracking servo and set the focus balance to ‘1’. Write down the approximate peak-to-peak signal value at this point (measurement A).
Change the focus balance to ‘0’. Switch the player into normal mode and search for frame 115. The frame should look like the following picture with minimal cross talk either side of the black bar (crosstalk will appear as a faint black bar approximately half-way between the centre bar and either edge of the screen):
Observe the crosstalk on the left and right hand sides of the screen. If the crosstalk is minimal and symmetrical, this adjustment is complete. If the crosstalk is not acceptable, adjust VR7 to achieve the minimum possible crosstalk.
Play the test disc in service mode again. Around frame 1,000 open the tracking servo and set the focus balance to ‘1’. Write down the approximate peak-to-peak signal value at this point (measurement B). If the difference between A and B is within 30% (i.e. B / A >= 0.7) this adjustment is complete, otherwise repeat the procedure above by searching to frame 115 and repeating the procedure.
If it is not possible to get the signal difference within the expected range, perform the pick up tracking and tangential adjustment again, then repeat the focus error balance adjustment.