HOW TO REPAIR A DVD MECHANISM - DISASSEMBLE PROCEDURE - CD-DVD MECHANISMS [No power-Tray removal from the Bottom - No power-Tray removal from the Top]
Tray Movement
The loading motor moves the disc tray in or out. Without the
tray, the loading motor’s shaft is seen on the right side.
Top View
The rotation of the motor turns the three gears to its left.
The final gear at the far-left mates with the teeth on the tray. Motor
direction determines
tray movement. Electrical feedback to stop the motor is an
opened/closed electrical switch under the white activator arm. The tray at the
end position pushes the arm.
Platform Position
When the loading motor drives the tray inward, a channel in
the tray moves a spring-loaded pawl into the middle rotating gear. The gear’s
rotation continues to slide this pawl to the left. The front part of this pawl
that faces the laser assembly platform lifts a pin connected to the platform.
As the pawl slides left, the platform is lifted up. The pawl in the tray’s
channel prevents the tray from sliding out.
No Power Tray Removal – From the Bottom
A spring-loaded pawl
under the tray locks the tray closed. The bottom part of this pawl can be
accessed from under the mechanism assembly.
- Unplug AC power and press the power button to discharge the power supply capacitors.
- At the mechanism top, remove the two screws and the mechanism’s top cover. The cover acts as a tray stop. Cover removal allows the tray to be pulled out later.
- At the rear of the mechanism remove the rear black screw for finger clearance.
- Place your finger under the mechanism. Push the slider’s bottom tab.
- At the bottom of the assembly, slide the tab toward the center of the mechanism. This lowers the laser (unchucks), freeing the tray.
- From the top of the mechanism, slide the tray out.
- Remove the two screws and the mechanism’s top cover to expose the tray and laser platform.
- Locate the top pawl under the tray by inserting a small screwdriver between the platform and tray. The pawl is just in front of the spindle motor.
- Slide the pawl to the right to lower the platform and free the tray.
- Remove the tray.
Maximum RF output level occurs when the laser beam is
perpendicular to the disc’s information layer. The tilt motor raises one end of
the laser platform so its beam is perpendicular to the disc.
Access and Operation
The tilt motor is a stepping motor located next to the
incline gear. At power OFF, the incline gear lowers one end of the laser
platform. At power ON, the incline gear raises the platform to full
height. The stepping motor then increments the incline gear to the
middle position. This position is stored in EEProm IC201 and updated during the
test mode automatic adjustments. During DVD playback, if the RF level
fluctuates, the tilt motor rotates until the RF level stabilizes. The incline
gear remains at the middle position during CD playback.
Sled Position
The sled motor moves the laser assembly away from home
position at the spindle motor. The laser assembly‘s home position is marked as
it blocks the light to a photo detector sensor. This picture
shows the photo sensor location under the sled motor shaft.
Focus Coil
Voltage applied to the focus coil that is connected to the
lens opposes a stationary vertical magnet. The force generated moves the
objective lens up or down to focus the laser spot on the information layer of
the disc.
CLICK ON PICTURES TO ZOOM
Laser
A ribbon cable connects the laser assembly to its circuit
board. A circuit board connector clamps the assembly’s ribbon cable. Free the
cable from the connector by pulling the connector tabs on both
sides 1mm toward the cable. The connector will slide out. In the picture the
left side of the cable is free from the connector. In a replacement laser assembly, a spot of solder is placed
on the foils of the ribbon cable (see the focus coil picture) to protect the
laser diode from static damage that will shorten its life. Remove the solder
spot AFTER connecting the laser assembly cable to the circuit board.
