50
No Audio
If the disc is spinning and the LOCK test point is HIGH, the servos are
working. Audio should output Servo Control if the RF data is valid, and
the IC is OK. Servo Control outputs two clues about the audio produced:
• FL display information (tracks, time elapse)
• L & R Audio Output
The SQ information updates the display with running time information.
The analog audio output goes to buffers and a mute stage before arriving
at the rear panel output jacks.
There is also a line output mute inside Servo Control. If the degree of
errors in recovering the audio data is high, there is no SQ or line output.
Audio recovery can be monitored at the C2PO test point. This point is
LOW when digital to audio processing is correct. If the servos are work-
ing (LOCK = HIGH), there is no reason C2PO will be HIGH (defective)
unless the disc is scratched or the Servo IC is defective. In the CD
Starting Waveform, the + pulses at the right of the C2PO waveform des-
ignate disc scratches, causing uncorrectable errors.
CD Playback Starting C2PO tp
Signal Name Location
C2PO test point IC101/pin 19
Time base = 200msec/div
Scope ground is taken at Vc (IC103/pin 12)
CH1 2.00 V=
CH2!5.00 V=
CH3!5.00 V=
CH4!5.00 V= CHP MTB 200ms- 2.28dv ch1+
4
Disc Scratches
Syscon
FL
Display
Driver
Data
C2PO
Display
SQ
Mute /
Buffers
Line Out
IC SW
Audio Out
Servo
Control
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