Maintenance Of Laser Pickup - Jvc Xl-V222Bk Service Manual

Maintenance of Laser Pickup
(1) Laser diode life check
XL-V222BK
When the service life of the laser diode has expired, the (2) The drive current required by the laser diode will be
following symptoms will appear. increased.
(1) The level of RF output (EFM output: amplitude of eye In such a case, check the service life of the laser diode
pattern) will be lowered. following the flowchart below.
Is RF output
more than 0.5 Vp-p?
0.4 Vp-p, for example..
1.0 Vp-p, for example.
Is the laser
diode drive current less
than 120 mA?
130 mA, for example.
60 mA, for example.
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(2) Measurement of laser diode drive current
Cut the jumper wire (W710) shown in the figure on the
right using pliers, etc., and solder a 1-ohm resistor between
the two ends.
Measure the voltage across the resistor with a millivoltmeter.
When the voltage is more than 120 mV, it shows that the
service life of the laser diode has expired.
(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.
LJ rin millivoltmeter
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