Focus Bias Adjustment - Sony MDS-SP55 Service Manual

9. Press the ENTER/YES button, and save the adjustment results
in the non-volatile memory. ("MD EFB =
displayed for a moment.)
10. "MD EFB = MO-P". will be displayed.
The optical pick-up moves to the pit area automatically and
servo is imposed.
11. Rotate the l L knob until the waveform of the oscillo-
scope moves closer to the specified value.
In this adjustment, waveform varies at intervals of approx. 2%.
Adjust the waveform so that the specified value is satisfied as
much as possible.
(Traverse Waveform)
VC
Specification A = B
12. Press the ENTER/YES button, and save the adjustment results
in the non-volatile memory. ("MD EFB =
displayed for a moment.)
Next "MD EF MO ADJUST" is displayed. The disc stops rotat-
ing automatically.
13. Press the A button and remove the disc.
14. Load the check disc (MD) TDYS-1.
15. Roteto l L knob and display "MD EF CD ADJUST".
16. Press the ENTER/YES button and display "MD EFB =
CD". Servo is imposed automatically.
17. Rotate the l L knob so that the waveform of the oscil-
loscope moves closer to the specified value.
In this adjustment, waveform varies at intervals of approx. 2%.
Adjust the waveform so that the specified value is satisfied as
much as possible.
(Traverse Waveform)
VC
Specification A = B
18. Press the ENTER/YES button, display "MD EFB =
for a moment and save the adjustment results in the non-volatile
memory.
Next "MD EF CD ADJUST" will be displayed.
19. Press the A button and remove the check disc (MD) TDYS-1.
Note 1 : MO reading data will be erased during if a recorded disc is
used in this adjustment.
Note 2 : If the traverse waveform is not clear, connect the oscillo-
scope as shown in the following figure so that it can be
seen more clearly.
330 kΩ
BD board
CN110 pin 3 (TE)
CN110 pin 1 (VC)
28
SAVE" will be
A
B
SAVE" will be
A
B
SAVE"
Oscilloscope
10pF

5-12. FOCUS BIAS ADJUSTMENT

Adjusting Procedure :
1. Load a test disk (MDW-74/GA-1).
2. Rotate the l L knob and display "MD CPLAY MODE".
3. Press the ENTER/YES button and display "MD CPLAY MID".
4. Press the MENU/NO button when "MD C1 =
is displayed.
5. Rotate the l L knob and display "MD FBIAS ADJUST".
6. Press the ENTER/YES button and display "MD
".
The first four digits indicate the C1 error rate, the two digits
after [/] indicate ADER, and the 2 digits after [a =] indicate the
focus bias value.
7. Rotate the l L knob in the clockwise direction and find
the focus bias value at which the C1 error rate becomes 220
(Refer to Note 2).
8. Press the ENTER/YES button and display "MD
".
9. Rotate the l L knob in the counterclockwise direction
and find the focus bias value at which the C1 error rate becomes
220.
10. Press the ENTER/YES button and display "MD
".
11. Check that the C1 error rate is below 50 and ADER is 00. Then
press the ENTER/YES button.
12. If the "( " in " - - ( " is above 20, press the ENTER/
YES button.
If below 20, press the MENU/NO button and repeat the
adjustment from step 2.
13. Press the A button to remove the test disc.
Note 1 : The relation between the C1 error and focus bias is as
shown in the following figure. Find points a and b in the
following figure using the above adjustment. The focal
point position C is automatically calculated from points a
and b.
Note 2 : As the C1 error rate changes, perform the adjustment us-
ing the average vale.
C1 error
220
b
c
AD = "
/ a =
/ b =
/ c =
a Focus bias value
(F. BIAS)