Sony MDS-JB920 Check Prior to Repairs, Temperature Compensation Offset Check, Laser Power Check

+

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oscilloscope (DC range)

6. CHECK PRIOR TO REPAIRS

These checks are performed before replacing parts according to “approximate specifications” to determine the faulty locations. For details, refer to “Checks Prior to Parts Replacement and Adjust- ments” (See page 8).

6-1. Temperature Compensation Offset Check

When performing adjustments, set the internal temperature and room temperature of 22 °C to 28 °C.

Checking Procedure:

1.Rotate the [ÊÊÊÊÊÊÊÊAMSÊÊÊÊÊÊÊÊ]- ± knob to display “TEMP CHECK”.

2.Press the [YES] button.

3.“T=@@(##) [OK” should be displayed. If “T=@@ (##) [NG” is displayed, it means that the results are bad.

(@@ indicates the current value set, and ## indicates the value written in the non-volatile memory.)

6-2. Laser Power Check

Before checking, check the IOP value of the optical pick-up. (Refer to 5-8. Recording and Displaying IOP Information.)

Connection :

laser

power meter

Optical pick-up objective lens

digital voltmeter

BD board
CN110 pin 5	(I +3V)
		+
CN110 pin 4	(IOP)		–

Checking Procedure:

1.Set the laser power meter on the objective lens of the optical pick-up. (When it cannot be set properly, press the [ÊÊÊÊÊÊ]0 but- ton or [ÊÊÊÊÊÊ]) button to move the optical pick-up.)

Connect the digital volt meter to CN110 pin 5 (I+3V) and CN110 pin 4 (IOP).

2.Then, rotate the [ÊÊÊÊÊÊÊÊAMSÊÊÊÊÊÊÊÊ]- ± knob and display “LDPWR CHECK” (C02).

3.Press the [YES] button once and display “LD 0.9 mW $ ”. Check that the reading of the laser power meter become 0.84 to 0.92 mW.

4.Press the [YES] button once more and display “LD 7.0 mW $

”. Check that the reading the laser power meter and digital volt meter satisfy the specified value.

Specification:

Laser power meter reading: 7.0 ± 0.2 mW

Digital voltmeter reading : Optical pick-up displayed value ±10%

(Optical pick-up label)

KMS260A

27X40 B0567

lOP=56.7 mA in this case

lOP (mA) = Digital voltmeter reading (mV)/1 (Ω)

5.Press the [MENU/NO] button and display “LDPWR CHECK” and stop the laser emission.

(The [MENU/NO] button is effective at all times to stop the laser emission.)

Note 1: After step 4, each time the [YES] button is pressed, the display

will be switched between “LD 0.7 mW $			”, “LD 6.2 mW $
”, and “LD Wp	$	”. Nothing needs to be performed
here.

6-3. Traverse Check

Note 1: Data will be erased during MO reading if a recorded disc is used in this adjustment.

Note 2: If the traverse waveform is not clear, connect the oscilloscope as shown in the following figure so that it can be seen more clearly.

BD board

330 k Ω

CN110 pin 3 (TE)

CN110 pin 1 (VC) 10 pF

Connection :

oscilloscope (DC range)

BD board
CN110 pin 3	(TE)	+	V: 0.1 V/div
CN110 pin 1	(VC)
		–	H: 10 ms/div

Checking Procedure:

1.Connect an oscilloscope to CN110 pin 3 (TE) and CN110 pin 1 (VC) of the BD board.

2.Load a disc (any available on the market). (Refer to Note 1.)

3.Press the [ÊÊÊÊÊÊ]) button and move the optical pick-up outside the pit.

4.Rotate the [ÊÊÊÊÊÊÊÊAMSÊÊÊÊÊÊÊÊ]- ± knob and display “EF MO CHECK”(C03).

5.Press the [YES] button and display “EFB = MO-R”. (Laser power READ power/Focus servo ON/tracking servo OFF/spindle (S) servo ON)

6.Observe the waveform of the oscilloscope, and check that the specified value is satisfied. Do not rotate the[ÊÊÊÊÊÊÊÊAMSÊÊÊÊÊÊÊÊ]- ± knob.

(Read power traverse checking)

(Traverse Waveform)

A

VC

B

Specified value : Below 10% offset value

Offset value (%) = IA – BI X 100 2 (A + B)

7.Press the [YES] button and display “EFB = MO-W”.

8.Observe the waveform of the oscilloscope, and check that the specified value is satisfied. Do not rotate the [ÊÊÊÊÊÊÊÊAMSÊÊÊÊÊÊÊÊ]- ± knob.

(Write power traverse checking)

(Traverse Waveform)

A

VC

B

Specified value : Below 10% offset value

Offset value (%) = IA – BI X 100 2 (A + B)

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