Denon DCD-3520 Service Manual page 15

Cautions for Handling the Laser Pick-up
The laser pick-up KSS-151A is assembled and precisely
adjusted using a sophisticated manufacturing process in our
plant. Do not disassemble or attempt to readjust it. Please
keep the following instructions carefully in handling pick-
up.
1. Handle with Care
(1) Storage
Do not store the pick-up in dusty, high-temperatured
or high-humidity environments.
2. Laser Diode (LD)
(1) Protect your eyes
The laser beam may damage the human eye, since the
intensity of the focused spot may reach 7 x 10° W/
cm? even if the intensity at the objective lens is
400 uW maximum. As the light beam spreads after
focused through the objective lens, it does not effect
you in the place as far as more than 30 cms. However,
do not look at the laser light beam either through the
objective lens directly nor another lens or a mirror.
(2) Poison of As
Since the LD chip contains As (Arsenic), as GaAs +
GaAlAs, as Known as the poison, although the poison
is relatively weak, in comparing with others, e.g.
As,O;, AsCl, etc., and the amount is small, avoid
putting the chip in acid or an alkali solution, heating
it over 200°C or putting it into your mouth.
(3) Avoid surge current or electrostatic discharge
The LD may be damaged or deteriorated by it's own
strong light if a large current is supplied to it, even if
only a short pulse.
Make sure that there is no surge current in the LD
driving circuit by switches or else. Be careful to handle
pick-up as it may be damaged in a moment by human
electrostatic discharge. The pins of the LD are short-
circuited by solder for protection during shipment.
For safety handling of an LD, grounding the human
body, measuring equipments and jig 1s strongly recom-
mended. And still it is further desirable to make use of
mat on the platform and floor for handling the LD.
To open the short circuit, remove the soldering quickly
with a soldering iron whose metal part is grounded.
The temperature of the soldering iron should be less
than 320°C (30W).
3. Actuator
(1) The performance of the actuator may be effected if
magnetic material is located nearby, since the actuator
has a strong magnetic circuit. Do not permit dust to
enter through the clearance of the cover.
(2) Cleaning the lens
It may change the specifications by attaching dust or
ash on the object lens. Clean the lens with a cleaning
paper dampened a little water, not pressing lens with so
much strength by the cleaning paper.
4. Metal Bearing
As the metal bearing of Cu-compound sintered alloy is
impregnated with FROIL946P(*Part No. 529 0054 007),
never fail to supply the bushing with the same jubricant at
the time of replacing the pick-up.
5. Handling
Please handle the laser pick-up with holding the slide base
(rosin molded part).
When either a part of human body or some other things
may happen to touch directly with the circuit part of P.W.
Board, it may cause deterioration, take careful attention in
handling this base.
6. Deterioration
When difficulty occurs either in focus or tracking adjust-
ment nor able to adjust the focus or tracking, it seems that
the laser pick-up is deteriorated. In these cases, check a
value of {aser diode current and give a decision for
deterioration.
7, Fundamental Deterioration Decision of Laser Pick-up
(1) {if a voltage value in between No. 2 and No. 6 pins of
TP102 of the servo and signal processor unit, the value
of laser diode current ''iop'' can be found by a formula
ML
22
(2) If an "iop'' exceeds +10% compared with the !OP
indication on the laser pick-up nameplate, there is a
fair chance for deterioration when it is checked under
"iop1" =
a Circumambient temperature 23°C.
(3) When the circumambient temperature changes =10°C,
"jop 1" will change +5%. The "iop1" will also be
changed by the passage of time.
(4) In case of the above conditions taking into considera-
tion and performed the adjustment in proper way, if
the HF level at pin No. @) of TP102 on Main Unit,
and in between GND4 becomes 1V or lesser values, or
ajitter occurs great, the laser pick-up may be deterio-
rated.
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