JVC KD-S5050 Service Manual page 26

5.5 Signal processing section
Is the sound output from
both channels (L, R)?
Normal
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.
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 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.
1-26 (No.MA026)
NO
No sound from either
YES
Is 9V present at IC301 pin
Is the audio signal
(including sampling output
components) output to
IC151 pins 1 and 7 during
Is the audio signal output
at IC301 pins 3 and 30
during playback?
Check the muting circuit.
NO
Replace it.
NO
channel.
YES
NO
31?
YES
NO
playback?
YES
NO
YES
5.7 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.
Check the eye-pattern at RF test point.
Compare the L-ch and
R-ch to locate the
defctive point.
Check the viciniyt of the
Q321 audio power
supply.
Check IC151 and its
peripheral circuits.
Check IC301 and its
peripheral circuits.
Play a disc.
Finish.