JVC KD-G311, Service Manual

Page: 28 / 79

1-28 (No.MA134)
5.6 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: amplitude of eye
pattern) will be low.
(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 la-
ser diode is almost worn out, and the laser pickup should
be replaced. If the semi-fixed resistor is adjusted while the
pickup is functioning normally, the laser pickup may be
damaged due to excessive current.
5.7 Replacement of laser pickup
Is RF output
1.0 0.35Vp-p?
YES
NO
OK
Replace it.
Replace the pickup with a normal one. (Refer
to "Removing the pickup unit" on the previous page.)
Plug the power cord in, and turn the power on.
At this time, check that the laser emits for about
seconds and the objective lens moves up and down.
Note: Do not observe the laser beam directly.
Play a disc.
Check the eye-pattern at
RF test point.
Finish.
Turn off the power switch and,disconnect the
power cord from the AC outlet.