JVC XM-P55 Service Manual page 25

Maintenance of MD Pickup
1. Cleaning of pickup lens
(1) Prior to changing the pickup, clean the pickup lens.
(2) For cleaning the lens, use the following cotton swab after
mearsing it in alcohol.
Product No. JCB-B4; Manufacturer;Nippon Cotton Swab
2. Confirmation of the service life of laser
diode when the service life of the laser
diode has been exhausted, the following
symptoms will appear.
(1) Recording will become impossible.
(2) The RF output (EFM output and eye pattern amplitude)
will become lower.
(3) The drive current required for light emitting of laser diode
will be increased.
Confirm the service life according to the following flow chart:
Can the laser power
adjust under test mode?
Is the power output
750
YES
Is the drive current
of laser diode
45mA or less?
YES
OK.
3. Method of measuring the drive current of
laser diode
When the voltage measured at the both side of carbon resistor
R301 on the MD servo P.C. board (VMW2424A) have become
45mV or over, the service life of the laser diode is judged to have
been exhausted.
NO
Change the pickup
NO
Change the pickup
Procedures of Changing
the MD pickup
Change the MD pickup by referring
to "Removing the MD pickup" in the
Disassembly Method.
Set the pickup to [TEST] mode according
to the procedures described in the
Adjustment Method.
Adjust the laser power 75
Adjust the disc.
Completion of changing the MD pickup.
Since this system is designed to perform magnetic
recording, the laser power ten times or over of the
conventional MD player will be output. Therefore, be
sure to perform not only adjustment and operation
of this system so carefully as not to directly look at the
laser beam or touch on the body.
4. Semi-solid state resistors on
the APC P.C. board
The semi-solid state resistor on the APC P.C.board
attached to the pickup is used for adjusting the laser
power. Since these resistor should be adjusted in
pair according to the characteristics of the optical
block, be sure not to touch on the resistors.
Since the service life of the laser diode will be
exhausted when the laser power is low, it is
necessary to change the pickup. Meanwhile, do not
pickup. Otherwise, the pickup will be damaged due
to over current.
XM-P55
XM-PJ1
.
How to operation
Return to feed .
Adjust the Pre D
have been become OK
Return to feed .
Adjust the Mo D
have been become OK
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