Sony D-E451 Primary Service Manual Download Page 3

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The laser diode in the optical pick-up block may suffer electrostatic
breakdown because of the potential difference generated by the charged
electrostatic load, etc. on clothing and the human body. During repair,
pay attention to electrostatic breakdown and also use the procedure in
the printed matter which is included in the repair parts.
The flexible board is easily damaged and should be handled with care.

NOTES ON LASER DIODE EMISSION CHECK

The laser beam on this model is concentrated so as to be focused on the
disc reflective surface by the objective lens in the optical pick-up block.
Therefore, when checking the laser diode emission, observe from more
than 30cm away from the objective lens.

Before Replacing the Optical pick-up Block

Please be sure to check thoroughly the parameters as per the “Optical
pick-up Block Checking Procedure” (Part No. : 9-960-027-11) issued
separately before replacing the optical Pick-up block.
Note and specifications required to check are given below.

• FOK output : IC501

!™

When checking FOK, remove the lead wire to disc motor.

• S curve P-to-P value : 0.9 – 1.5Vp-p IC501

#¡

pin. (Connect pin

!™

of IC501 (TP880) and

of IC501 (GND) with a jumper wire).

When checking S curve P-to-P value, remove the lead wire to disc
motor.

• Adjusted part for focus gain adjustment : RV503
• RF signal P-to-P value : 0.8 – 1.2Vp-p
• Traverse signal P-to-P value : 1.0 – 2.4Vp-p
• The repairing grating holder is impossible.
• Adjusted part for tracking gain adjustment : RV502

SECTION 1

SERVICING NOTES

Fig. 1-2 Digital Voltmeter Connecting Location

NOTES ON HANDLING THE OPTICAL PICK-UP BLOCK OR
BASE UNIT

Method-2 (In the service mode or normal operation) :

Check the value of current flowing in the laser diode.

1. Remove the upper panel.
2. Read the current printed on the rear side of the optical pick-up.

(Print on the rear side of the optical pick-up)

3. Connect a level meter as shown in Fig. 1-2
4. Press the

key.

Fig.1-1 Method to push S801

A C 2 2 1 1 3 9 7

year

version

month

A : less than 48 mA

current value

date

line No.

shift No.

5. Calculate the current value by the reading of the digital voltmeter.

Reading of the tester (V) ÷ 4.7 (

Ω

) = current value (A)

(Example) Reading of the digital voltmeter of 0.2256 V :
0.2256 V ÷ 4.7

Ω

= 0.048 (A) = 48 mA

6. Check that the current value is within the following range.

• Current value of the label

-11

mA(25

Variation by temperature : 0.4mA /

Current increases with temperature increased.
Current decreases with temperature decreased.

If the current is more than the range above, there is a trouble in the
automatic power control circuit or the laser diode is in deterioration.
If less than the range, a trouble exists in the automatic power control
circuit or the optical pick-up.

[MAIN BOARD] (Side B)

S801

Laser Diode Checking Methods

During normal operation of the equipment, emission of the laser diode
is prohibited unless the upper panel is closed while turning ON the S801
(push switch type).
The following two checking methods for the laser diode are operable.

Method-1 (In the service mode or normal operation) :
Emission of the laser diode is visually checked.

1. Open the upper lid.
2. Push the S801 as shown in Fig. 1-1 .
3. Check the object lens for confirming normal emission of the laser

diode. If not emitting, there is a trouble in the automatic power
control circuit or the optical pick-up. During normal operation, the
laser diode is turned ON about 2.5 seconds for focus searching.

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