Pioneer CDX-FM653 Service Manual page 37

6.2 CHECKING THE GRATING
- Checking the Grating After Changing the Pickup Unit
• Note :
CD mechanism modules the grating angle of the pickup unit cannot be adjusted after the pickup unit is changed.
The pickup unit in the CD mechanism module is adjusted on the production line to match the CD mechanism
module and is thus the best adjusted pickup unit for the CD mechanism module. Changing the pickup unit is thus
best considered as a last resort. However, if the pickup unit must be changed, the grating should be checked
using the procedure below.
• Purpose :
To check that the grating is within an acceptable range.
• 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 track searching taking a long time, may appear.
• Method :
• Measuring Equipment
• Measuring Points
• Disc
• Mode
CD CORE UNIT
• Checking Procedure
1. Enter Test mode, then switch the 5V regulator on.
2. Using the TRACK+ and TRACK- buttons, move the pickup unit to the innermost track.
3. Press key PAUSE to close focus, the display should read "91". Press key PAUSE 2 times. Enter Rough Servo
mode. Press key ADJ to implement the tracking balance adjustment the display should now read "81".
4. As shown in the diagram above, monitor the LPF outputs using the oscilloscope and check that the phase differ-
ence 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 pickup 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 aver-
age angle.
• Hint
Change the disc changes the clamp position and may decrease the "wobble".
• Oscilloscope, Two L.P.F.
• E, F, REFO
• ABEX TCD-784
• TEST MODE
L.P.F.
E
E
100kΩ
390pF
F
REFO
F
100kΩ
390pF
CDX-FM653
Ych
Xch
Oscilloscope
L.P.F.
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