5
EYE-PATTERN SIGNAL – JITTER MEASUREMENT
Measure the signal on the input of the Signal processor
using an analog oscilloscope. Please find the exact
measuring point in your Service Manual.
See below examples of the signal. Amplitude should read at
least 700mVpp using SBC444A.
good
bad
If the oscilloscope shows a signal like the ‘bad’ one, and/or
the amplitude decreases within 1 minute - the CD drive has
to be replaced.
6
CD DRIVE – LASER CURRENT MEASUREMENT
The laser current can be measured as a voltage drop on a
resistor. The resistor is marked in every Service Manual.
The value depends on the type of CD drive.
typical value most probably defect
VAMxxxx : 150-230mV ≥350mV
MCDxx : 170-230mV ≥300mV
DA1x : 210-250mV ≥350mV
DA2x : 175-200mV ≥250mV
Use SBC444A (CD-DA) for measurement.
7
CD DRIVE – OFFSET MEASUREMENT
The photodiodes of the CD-drive may have an offset. These
offsets have to be compensated by the signal processor.
High offsets can lead to poor playability of some CDs
(skipping tracks).
To measure the offset values, start the Service Test
Program - section “Focus Test” without a CD.
The offsets can be measured with a DC Millivoltmeter
directly on the connector (see drawing below). Pin
numbering varies from drive to drive.
The values from diode A-D should read 0±10mV.
Diodes E and F are less critical.
If one of the offsets is higher than ±10mV the CD drive has
to be replaced. Otherwise replace the Signal Processor.
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