38
• Note :
The grating angle of the PU unit cannot be adjusted after the PU unit is changed. The PU unit in the CD mechanism
module is adjusted on the production line to match the CD mechanism module and is thus the best adjusted PU
unit for the CD mechanism module. Changing the PU unit is thus best considered as a last resort. However, if the
PU unit must be changed, the grating should be checked using the procedure below.
• Purpose :
To check that the grating is within an acceptable range when the PU unit is changed.
• Symptoms of Mal-adjustment :
If the grating is off by a large amount symptoms such as being unable to close tracking, being unable to perform
track search operations, or taking a long time for track searching.
• Method :
• Measuring Equipment
• Measuring Points
• Oscilloscope, Two L.P.F.
• E, F, REFO1
• Disc
• ABEX TCD-782
• Mode
• TEST MODE
• Checking Procedure
1. In test mode, load the disc and switch the 3V regulator on.
2. Using the
→
and
←
buttons, move the PU unit to the innermost track.
3. Press key 3 to close focus, the display should read "91". Press key 2 to implement the tracking balance
adjustment the display should now read "81". Press key 3. The display will change, returning to "81" on the
fourth
press.
4. As shown in the diagram above, monitor the LPF outputs using the oscilloscope and check that the phase
difference is within 75
°
. Refer to the photographs supplied to determine the phase angle.
5. If the phase difference is determined to be greater than 75
°
try changing the PU unit to see if there is any
improvement. If, after trying this a number of times, the grating angle does not become less than 75
°
then the
mechanism should be judged to be at fault.
• Note
Because of eccentricity in the disc and a slight misalignment of the clamping center the grating waveform may be
seen to "wobble" ( the phase difference changes as the disc rotates). The angle specified above indicates the
average angle.
• Hint
Reloading the disc changes the clamp position and may decrease the "wobble".
100k
Ω
390pF
100k
Ω
390pF
E
VREF
F
VREF
Xch
Ych
L.P.F.
L.P.F.
REFO1
F
E
CD CORE UNIT(S10)
Oscilloscope
1
2
3
4
1
2
3
4
F
E
D
C
B
A
DEH-P2550/XM/ES
6.2 CHECKING THE GRATING AFTER CHANGING THE PICKUP UNIT
Summary of Contents for DEH-P2550 XN/ES
Page 4: ...1 SPECIFICATIONS 4 1 2 3 4 1 2 3 4 F E D C B A DEH P2550 XM ES Backup current 5 mA or less ...
Page 6: ...6 1 2 3 4 1 2 3 4 F E D C B A DEH P2550 XM ES 2 2 EXTERIOR ...
Page 18: ...18 1 2 3 4 1 2 3 4 F E D C B A DEH P2550 XM ES 3 3 KEYBOARD UNIT C C KEYBOARD UNIT CAW1759 ...
Page 26: ...26 1 2 3 4 1 2 3 4 F E D C B A DEH P2550 XM ES A A TUNER AMP UNIT IC Q ...
Page 27: ...27 5 6 7 8 F E D C B A 5 6 7 8 DEH P2550 XM ES A SIDE B ...
Page 55: ...55 5 6 7 8 F E D C B A 5 6 7 8 DEH P2550 XM ES 8 OPERATIONS ...
Page 56: ...56 1 2 3 4 1 2 3 4 F E D C B A DEH P2550 XM ES ...
Page 57: ...57 5 6 7 8 F E D C B A 5 6 7 8 DEH P2550 XM ES ...
