JVC CH-X1500 Service Manual page 29

3.4 Maintenance of laser pickup
(1) Cleaning the pick up lens
Before you replace the pick up, please try to clean the lens
with a alcohol soaked cotton swab.
(2) Life of the laser diode
When the life of the laser diode has expired,the following
symptoms will appear.
• The level of RF output (EFM output:ampli tude of eye
pattern) will be low.
Is RF output
1.0 0.35Vp-p?
YES
O.K
(3) Semi-fixed resistor on the APC PC board
The semi-fixed resistor on the APC printed circuit board
which is attached to the pickup is used to adjust the laser
power.Since this adjustment should be performed to
match the characteristics of the whole optical block, do not
touch the semi-fixed resistor. If the laser power is lower
than the specified value,the laser diode is almost worn out,
and the laser pickup should be replaced. If the semi-fixed
resistor is adjusted while the pickup is functioning normal-
ly,the laser pickup may be damaged due to excessive cur-
rent.
NO
Replace it.
3.5 Replacement of laser pickup
Turn off the power switch and,disconnect the
power cord from the ac outlet.
Replace the pickup with a normal one.(Refer
to "Pickup Removal" on the previous page)
Plug the power cord in,and turn the power on.
At this time,check that the laser emits for
about 3seconds and the objective lens moves
up and down.
Note: Do not observe the laser beam directly.
Play a disc.
Check the eye-pattern at TP1.
Finish.
CH-X1500
1-29