JVC KDS747
Service Manual

KD-S747

3.3 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.

3.4 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)

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.

Play a disc.

Check the eye-pattern at TP1.

Finish.

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