35
DEH-1450,1450B
• Note :
The grating angle of the PU unit cannot be adjusted after the PU unit is changed. The PU unit in the CD mecha-
nism 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
• Oscilloscope, Two L.P.F.
• Measuring Points
• E, F, VREF
• Disc
• ABEX TCD-784
• Mode
• TEST MODE
ence is within 75° . Refer to the photographs supplied to determine the phase angle.
4. 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.
• 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.
VREF
E
F
6.2 CHECKING THE GRATING AFTER CHANGING THE PICKUP UNIT
CONTROL UNIT
Oscilloscope
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