SONY DE455
Service Manual

Focus/Tracking Gain Adjustment A servo analyzer is necessary in order to perform this adjustment exactly. However, this gain has a margin, so even if it is slightly off, there is no problem. Therefore, do not perform this adjustment. Focus/tracking gain determines the pick-up follow-up relative to mechanical noise and mechanical shock when the 2-axis device operate. However, as these reciprocate, the adjustment is at the point where both are satisfied. � When gain is raised, the noise when 2-axis device operates increases. � When gain is lowered, it is more susceptible to mechanical shock and skipping occurs more easily. This adjustment has to be performed upon replacing any of the following parts : � Optical pick-up � RV503 (Focus gain) � RV502 (Tracking gain) Normally, be sure not to move RV503 (focus gain) and RV502 (tracking gain).
C598 C503 48 C108 TP547

� Focus Gain Adjustment � Procedure : This adjustment is not performed. If focus gain RV503 is turned, set to mechanical center. � Tracking Gain Adjustment � (perform at normal operation)
[MAIN BOARD] (Side B)

1. Place the optical pick-up level, horizontally. (If the optical pickup is not level, the 2-axis device will be weighted and adjustment cannot be done.) 2. Connect the oscilloscope between TP514 (TEO) and TP533 (VC) on the MAIN board. 3. Set the disc (YEDS-18) and Press the ^ (+) key. 4. Turn RV502 slightly clockwise (tracking gain drops) and obtain a waveform with a fundamental wave (waveform has large waves) as in Figure 5-1 . 5. Turn RV502 slowly counterclockwise (tracking gain rises) until the fundamental wave disappears (no large waves) as in Figure 5-2. 6. Set RV502 to the position about 30 °counterclockwise from the position obtained in step 5. If RV502 contact point is more than 90 ° counterclockwise from mechanical center, tracking gain is too high. In this case, readjust from step 4. 7. Press ^ (+) or = keys and observe the 100 track jump waveform. Check that no traverse waveform appears for both ^ (+) or = directions. (See Figures 5-3 and 5-4.) It is acceptable if the traverse waveform appears only now and then, but if it appears constantly raise tracking gain slightly and check step 7 again. 8. Check that there is no abnormal amount of operation noise (white noise) from the 2-axis device. If there is, tracking gain is too high, readjust starting with step 4. The waveforms are those measured with the oscilloscope set as shown below. � VOLT/DIV : 50mV � TIME/DIV : 5mS � Waveform when tracking gain lowered. Fundamental wave appears (large waves).
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TP514 (TEO) TP533 (VC)
TP102 FB101 D105 C105

C205

D804

oscilloscope (DC range)

Fig. 5-1 � Waveform when fundamental wave disappears (no large waves).
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807 C520

TP306

Q101 Q201 D205

Fig. 5-2 � Waveform when no traverse waveform during 100 track jump. (Brake application is smooth because of adjustment.)

C208 L502

TP302 TP202

FB302
FB201 R521 TP521 TP522TP515TP508

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TP507 Q501 C525 R512 TP514 R519 C514 TP503 C501 (TEO) R517 TP509 TP502 TP511 R501 TP533 0 TP534 TP512 32 30 25 C599 R504 (VC) C517 R505 TP523 1 TP506 24 11 C512 IC501 20 C505 TP513 TP504 5 (RFO) C510 C506 17 8 C513 TP540 R549 C504 L508 C571

R502

R503

Fig. 5-3
100 track jump waveform

� Waveform when no traverse waveform during 100 track jump. (Brake application is poor because of adjustment.)

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100 track jump waveform traverse waveform

Fig. 5-4

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