JVC KDS5050
Service Manual

5.5

Signal processing section

Is the sound output from both channels (L, R)? YES Normal

NO

No sound from either channel. YES Is 9V present at IC301 pin 31? YES Is the audio signal (including sampling output components) output to IC151 pins 1 and 7 during playback? YES Is the audio signal output at IC301 pins 3 and 30 during playback? YES Check the muting circuit.

NO

Compare the L-ch and R-ch to locate the defctive point.

NO Check the viciniyt of the Q321 audio power supply. NO

Check IC151 and its peripheral circuits.

NO

Check IC301 and its peripheral circuits.

5.6

Maintenance of laser pickup

5.7

Replacement 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.

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)

Is RF output 1.0 0.35Vp-p?

NO Replace it. 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.

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. 1-26 (No.MA026)

Play a disc.

Check the eye-pattern at RF test point.

Finish.