JVC KD-S550, Service Manual

Page: 11 / 41

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.
(1) The level of RF output (EFM output:ampli
tude of eye pattern) will be low.
Replacement of laser pickup
Is RF output
1.0 0.35Vp-p?
Replace it.
NO
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 normally,the laser
pickup may be damaged due to excessive current.
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.