Denon UCD-250 - UNIT MECHANISM SERVICE PROCEDURES; Unit Mechanism Removal and Servicing; Lens and Laser Inspection

27
2,
(1)
1)
2)
M2 x 3
binding screw
(Tightening torque:
Removal of the unit mechanism (Fig. 7)
After removing the loading mechanism, remove the tab of the
bottom surface (in one location) as illustrated in Fig. 7.
©3 mm dia. x 16 CT binding screw
SY
Unit mechanism
Fig. 7
To replace the DC motor (D2) and the turntable, follow the
procedure below .
Pull the turntable (plastic) off vertically from the unit plate.
When fitting on the servicing turntable (metal), make a height
adjustment. (Fig. 8)
Do not exert excessive force to the shaft of the DC motor (D2) at this
time.
Set screw with hexagonal
hole (3 mm dia.)
4 to 6kg)
25.4
4 to 6kg)
For the dimensions at parts marked “2X”, adjust the
height using the turntable height JIG.
JIG No.: SGK-0030
Fig. 8
3) At the time of service replacement of the DC motor (D2), do not
apply excessive force in direction B. When part C of the unit plate
is misshapen, it will cause eye pattern deterioration. (Fig. 9)
Part C Direction B
$ $ Part C
Unit plate
(Tightening torque:
NOTE:
e@ Motor replacement or turntable replacement method
Remove the pressure-fitted turntable, and remove the
motor screws.
e@ Do not reuse a turntable (plastic) that has been removed
once.
(2) When disassembling and assembling the unit mechanism,
assemble with wiring resembling that of Fig. 10
Inspection of the objective lens (Fig. 11)
Handle so as not to get dirt or dust on the objective lens of the lens
actuator section. Note that when used for a long period, dirt or dust
may have adhered to the objective lens. Try cleaning the surface of
the objective lens with a dry, clean cotton swab.
If the dirt still does not come off, moisten the cotton swab with a
small amount of water and wipe. When doing this, be careful not to
get water on any parts other than the lens.
af:
{
Dise turntable
Lens actuator section
Objective lens
Fig. 11
Inspection for laser breakdown
The laser is normally driven with a current of 30 to 80 mA. If this
laser drive current value is measured at 120 mA or higher in the
circuit, the laser may be thought to be faulty. (The current value is
measured by taking the voltage (0.99 to 3.3 V) across both ends of
R401, which is 33 ohms).
5.
(1)
(2)
Precautions at time of servicing (Fig. 12)
Semiconductor laser
The semiconductor laser is very susceptible to static electricity
destruction and surge currents. Be careful never to touch the
terminals of the semiconductor laser and the terminals of the
flexible board with your hands or a tool.
As illustrated in Fig. 12, the current and light intensity character-
istics increase abruptly once the threshold current value is
exceeded.
Also note that this threshold current differs a little from laser to
laser. In view of this, when replacing the unit mechanism or any
work that involves setting the amount of light of the laser, be sure
to turn the adjustment control VR401 fully in the counterclockwise
direction, and then raise it to the specified value.
Intensity used
Light intensity —=
—= Current
Threshold current value
Fig. 12
Handing the unit mechanism (Fig. 13)
When
handling
the
pickup
mechanism
and
the
unit
mechanism,
use
a
ground
ring
such
as
the
one
illustrated
in
Fig.
13.(A
ground
ring
can
be
constructed
using
ordinary
lead
wire.)
Ground ring (lead wire)
Connect to pickup case
Resistor
of
1
to
10
Mohms
14
Fig. 13
Connect to chassis (Ground)
6.
D-250 a
CD PLAYER SECTION
Inspection of the actuator (Fig. 14)
Check the resistance value of the actuator coil. It is normal if the
values are as follows:
Focusing coil
Tracking coil
If the coils are open or shorted, the actuator may be thought to be
broken. Also, a 1.5 V battery can be used to observe if the lens
moves.
AF direction
Fig. 14