Measurement; Judging Step; Measuring Method - Denon DVD-3910 Service Manual

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op Measurement (Judging for Traverse Unit Replacement)
As to deciding whether optical pickup is defect or not (for replacing traverse unit), follow the steps below.

1. Judging Step

(1) Disc play abnormal
Problems such as disc no read, unsteady playback, etc.
(2) Laser drive current (Iop) check
Check Iop according to the measuring method described in step 2 below.
If the checked value is 1.5 times or more than the initial Iop indicated
on the rear of mechanism unit, the traverse unit should be replaced.
(3) Replacing traverse unit
Referring to "How to Replace Traverse Unit", replace the traverse unit.
No mechanism adjustment is required as the whole unit is replaced with
a new one.
2. op Measuring Method
DVD laser drive current measuring points
[DVD] Iop silk point
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CD laser drive current measuring points
[CD] Iop silk point
(1) DVD laser drive current measurement
• Playback the title-1/chapter-1 of DVDT-S01 or commercially available DVD disc.
• Connect an oscilloscope to the test point above and measure the voltage.
• DVD laser drive current is calculated by:
Iop = Measured Voltage Value / 14 (Resistance Value)
w w w
(2) CD laser drive current measurement
• Playback the track-1 of TCD-784 or commercially available CD disc.
• Connect an oscilloscope to the test point above and measure the voltage.
.
• CD laser drive current is calculated by:
Iop = Measured Voltage Value / 12 (Resistance Value)
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DVD mA
CD mA
Laser current initial value on the rear of mechanism
GU-3512 P.W.B. (foil side)
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y
i
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8 9
Iop
1.
(1)
(2) Iop
2 Iop
1.5
(3)
2. Iop
DVD laser drive current measuring points
[DVD] Iop silk point
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CD laser drive current measuring points
[CD] Iop silk point
(1) DVD
DVDT-S01 DVD
DVD
c o
(2) CD
.
TCD-784 CD
CD
11
2 4 9 8 2
DVD mA
mA
CD
Laser current initial value on the rear of mechanism
5 0 8 9 2 4 9 8 2
GU-3512 P.W.B. (foil side)
1 1
m
1
DVD-3910
9 9
9 9