Denon UCD-250 - LASER CIRCUIT HANDLING; Laser Control Circuit Precautions; Wiring and Handling Guidelines; Semiconductor Laser Safety

D-250
CD PLAYER SECTION
® Precautions in Use
Read the following carefully before handling.
1. Laser control circuit
The light output of the laser diode (LD) is greatly affected by temperature, so a built-in monitor photodiode should be used in the LD to supplement
the light output.
In order to get rid of the dispersion of the monitor photodiode, the semiconductor resistor accompanying the pickup has been adjusted so that the
mirror surface level of the HF signal becomes 250 mV when the measurement circuit of this manual and the basic laser drive circuit are used.
When designing a new laser drive circuit, note that the life of the laser will be shortened when the mirror level of the HF signal becomes 275 mV
with this measuring circuit.
2. Wiring
Be sure to use the specified connectors for the wiring.
Note that the eye pattern may deteriorate when there is a microprocessor or other digital noise source in the vicinity from the photodiode to the
harness.
Note that a poor connection related to the LD and actuator connector will cause deterioration of the laser, and so there should not be any looseness of
connectors.
® Precautions in Handling
This mechanism has been precisely assembled and adjusted at a special factory. It should not be disassembled or adjusted without good reason. Pay
attention to the following points related to handling.
1. General items
(1) Storage
Avoid storage in places with high temperatures and high humidity, and in places exposed to a lot of dust.
(2) Handling
The unit has been precisely adjusted and care should be taken so as not to expose the unit to shocks through dropping or careless handling.
2. Semiconductor taser (LD)
(1) Protection of the eyes from the laser
The output of the LD is via an objective lens and is a maximum of 400 uW, but reaches approximately 1.3 x 104W/cmg in places where there is
condensed light. After being condensed by the objective lens, the beam widens and so is all right at a distance of 30 cm or further, but during
operation the LD should never be allowed to be viewed directly or through another lens or mirror since this is dangerous.
(2) Destruction by surge currents or static electricity
When a large current flows through the LD, even for a very short period, the strong light which the LD generates itself will advance the
deterioration of the LD or destroy it.
Wire a switch into the LD drive circuit or provide another method of preventing the flow of surge currents. Also, when handied without
care, the LD can be destroyed instantly by the application of static electricity from the body. Therefore, when handling the LD, be sure to
ground your body and ground the measuring instruments, jigs, and tools. It is also desirable to use a grounding mat on the work bench and
floor.
3. Lens actuator
(1) The actuator section uses a strong magnetic circuit, so that when magnetic bodies come too close, their characteristics are altered.
Also be careful not to allow foreign matter to enter from the cover gap.
(2) Lens cleaning ,
Dust or dirt adhering to the objective lens will change the performance.
To clean, blow the dirt away with clean air from an air blower.
4. Handling
Be sure not to contact the lens when handling the LD.
Note that direct contact of the body or other objects with the circuit of the LD board will cause deterioration to occur, so sufficient care
should be taken.