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• Check the SSM signal (test point 78; pin 33)
=
Start-Stop turntable motor
- Motor start pulse when test point 78 is "high" for ;;,,
0.2
sec.
-
Motor stop pulse when test point 78 is "low" for
;;;o
0.2
sec.
Note:
After the motor start pulse, SWAB information
(Subcoding Word clock) will become visible at this point.
The period time of that signal is 136 µsec.
•
Check the subcode clock signals
-
Place a disc on the turntable.
- Select one of the following positions:
SERVICE POSITION 3 or position PLAY.
- Trigger the oscilloscope with the SWAB signal at test
point 78.
- Check the following signals:
SWAB at test point 78; pin 33
SCAB at test point 79; pin 35 (Subcode Clock
from Decoder-A to Filter-B)
SDAB at test point 80; pin 34 (Subcode Data
from Decoder-A to Fllter-B)
and their interrelations.
Note:
While the burst of 1 O clock pulses appear on SCAB
the a-channel information is transferred on SDAB.
Hereafter the P-bit indication follows.
The P-bit is "high" between two bursts of 1 O clock
pulses in case of pause indication and "low" in case of
music indication.
SWl<B
SDAB
_I--=
e
Check the CRI signal (pin 28)
MDA.00239
T12/638
The CRI signal is "low" in case of track jumping.
Player in position SEARCH.
cs
9 989
• Check the DEEM signal (test point 84: pin 32)
Place test disc 5 on the turntable.
4-7
- During playback of track no. 14 (recorded without
PRE-EMPHASIS), the DEEM signal should be "low".
- During playback of track no. 15 (recorded without
PRE-EMPHASIS), the DEEM signal should be "high".
VI. FIL TER-B IC
• Check the signals between Decoder-A IC and
Filter-B IC
- See sub.
"V.
Decoder-A IC":
• Check the X-tal signal
• Check the timing signals meant for Filter B
(WSAB, CL.AB, DAAB signals;
test points 71, 72 and
73).
• Check the EFAB signal (test point 74)
* Check the subcode clock signals
(SWAB, SCAB, SDAB signals; test points 78, 79 and
80).
• Check the
timing
signals
between
Fllter-B IC
and
DACIC
- Place a disc on the turntable.
- Select one of the following positions:
SERVICE POSITION 3 or position PLAY.
- Trigger the oscilloscope with the WSBD signal (Word
Select from Filter B to DAC) test point
85
(pin 18).
- Check the following signals:
WSBD at test point 85; pin 18
CLBD at test point 87; pin 16(Clock signal
from Filter B to DAC)
and their interrelation.
If an Audio Disc is used, there should be activity at
test point 86 (pin 15) DABD signal (DATA from Filter
B
to DAG).
If a disc with Digital Data (CD-ROM) is used, this point
is continuously switched "low" by transistor 6572.
WSBO
_ _ _ _ _ _ _ _ _ _,
176.lMHz
C L O O
= i
S S I M I
•
~
• Check the DOBM signal (Digital Output)
-
Place a disc on the turntable.
- Select the stand-by mode (only mains switch
depresed).
- Trigger the oscilloscope with the WSAB signal (test
point 71).
• Check the DOBM signal (test point 88: pin 14)
- An empthy audio signal has a fixed pattern. See
drawing "Stand-by".
- Select the PLAY mode.
Check the DOBM signal. See drawing "PLAY" .
.....
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