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4-6
V.
DECODER-A IC
•
Check the MC signal (pin 17; test point 12)
In stand-by mode, the MC signal (Motor Control)
corresponds to the figure below.
-
Place a disc on the turntable.
In position PLAY or SERVICE POSITION
3
the
MC'
signal corresponds to the figure below.
Ln_fl_
POSITION: STA~O
~
vlrL
POSrTION: PLAY IBEGINN!NGI
POSITION: PLAY !NORMAL!
38 8•9
A12
Note:
During start-up the duty cycle is 98%, then the duty cycle
of the signal becomes about
50%.
•
VC (connector point 15-1; test poirft 46)
- Place a disc on the turntable.
- The voltage at connector point 15-1 during playback
will be:
Yc=O>Vc>-1.7V
To check the turntable motor control, see C.D.M.-2
Service Manual: "Checking of the motor control".
•
Check the HFD-signal on test point 66, pin 26
-
Insert a disc.
- In the PLAY mode and in SERVICING POSITION
3
the
HFD-signal is "high"; however, minor pulses may be
present and in case of disorders on the disc.
In SERVICING POSITION 2 and during playback of
track no.
15
of test disc 5A HFD pulses are visible.
Position of the oscilloscope 5 ms/div.
r.'(')A.002.:tO
T07/7JJ
•
Check the CEFM signal (pin 27; test point
68)
-
Place a disc on the turntable.
-
In stand•by mode (only the mains switch is
depressed), the frequency lies between 2.82 MHz and
5.64 MHz.
-
In the position PLAY and SERVICE POSITION 2 and
3, the frequency is 4.32 MHz.
•
Check the Xin signal (pin 19; test point 69)
- The Xin frequency is 11.2896 MHz.
If this frequency deviates, check test point 70; Xout
signal, on Filter-8 IC.
This frequency should also be 11.2896 MHz.
•
Check the timing signals meant for Fllter-B IC
- Place a disc on the turntable.
- Select one of the following positions:
SERVICE POSITION 2 or 3, or position PLAY.
- Trigger the oscilloscope with the WSAB signal (test
point 71 ; pin 39).
- Check signals:
WSAB at test point 71 (pin 39)
(Word Select from Decoder-A to Filter-8)
GLAB at test point 72 (pin 38)
(Clock from Decoder-A to Filter-8)
and their interrelation.
- There must be activity a test point 73 (pin 37), DAAB
signal (DATA from Decoder-A to Filter-8).
•
Check the EFAB signal (Error Flag from Decocder-A
to Fllter-8) at test point 74 (pin 36)
- Place test disc 5A on the turntable.
- Select one of the following positions:
SERVICE POSITION
3
or position PLAY.
- During playback of track no. 17, a EFAB pulse should
appear at test point 61 for a short moment.
The EFAB pulses also appear when the disc is gently
slowed down and during fast search (Fast Forward or
Fast Reverse).
Note:
Filter-8 IC is capable of interpolating linearly
8
successive EFAB pulses.
I I I I-._
L . . . ,~i l l
period
"""-.!..
EFAB !errcr flogl
I I I I I ]
J
I
'38 St,.S A\2
•
Check the a-channel signals
-
Place a disc on the turntable.
- Select one of the following positions:
SERVICE POSITION
3
or position PLAY.
- Trigger on the ORA signal (0-channel Request
Acknowledge) test point 75; pin30.
- Check signals: QRA at test point 75 (pin 30)
OCL a test point 76 (pin 31)
(Q-channel-clock)
and their interrelation.
- There should then be activity at test point 77 (pin 29)
ODA (0-channel Data).
Note:
The ORA request is initiated by the µP (QRA "high").
Then Decoder-A answers this request (ORA goes "low").
With the next leading clock pulse (OCL) the ORA signal
is rendered "high" again by the
µP.
As soon as the µP has taken in enough information via
QDA, QRA will go low again. That is why the ORA times
vary each time.
cs
9 988
(
C
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