Philips CD304 MK II - Page 39

SCAB
SDAB
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
= 0.2 sec.
Note:
After the motor start pulse, SWAB information (Subco-
ding Word clock) will become visible at this point. The
period time of that signal is 136 psec.
Check the subcode clock signals
Place a disc on the turntable.
Select one of the following positions:
SERVICE POSITION B 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 Filter B)
and their interrelations.
Note:
While the burst of 10 clock pulses, appear on SCAB
the Q-channel information is transferred on SDAB. He-
reafter the P-bit indication follows.
The P-bit is "high” between two bursts of 10 clock pul-
ses in case of pause indication and “low” in case of
music indication.
= 2,.8224MHz
MDA.00239
Check the CRI signal
The CRI signal is “low” in case of track jumping.
Player in position SEARCH.
Check the DEEM signal (test point 84; pin 32)
Place test disc 5 on the turntable.
During playback of track no. 14 (recorded without
PRE-EMPHASIS), the DEEM signal should be “low”.
During playback of track no. 15 (recorded with PRE-
EMPHASIS), the DEEM signal should be "high’”.
Hl FILTER-B IC
@ Check the signals between Decoder-A IC and Fil-
ter-B IC
- See sub. "Il Decoder-A IC”:
* Check the X IN signal (test points 69 and 70)
* Check the timing signals meant for Filter B
(WSAB, CLAB, 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 Filter-B IC and
DAC IC
- Place a disc on the turntable.
- Select the foliowing position:
position PLAY.
- Trigger the oscilloscope with the WSBD signa! (Word
Select from Filter B to DAC) test point 85 (pin 18).
Check the following signats:
WSBD at test point 85; pin 18
CLBD at test point 87; pin 16 (Clock signal from Fil-
ter B to DAC) and their interrelation.
lf an Audio disc is used, there should be activity at test
point 86 (pin 15) DABD signal (DATA from Filter B to DAC).
If a disc with Digital Data (CD-ROM) is used, this point is
continuously switched “low” by transistor 6315. In that
case the word "data” appears on the display.
ee ESE
Hi 176.4 KHz
5.6448MHz
acd
UUUUUUUUUULU
UU
SWAB
D08M
SWAB
D0BM
ihe a 283uS _ an
_ a 5.66uS 2 b.
@ Check the DOBM signal (Digital Output)
- Place a disc on the turntable.
- Select the stand-by mode (only mains switch depres-
sed).
- Trigger the oscilloscope with the SWAB signal (test
point 78).
- Check the DOBM signal (test point 88; pin 14).
An empty audio signal has a fixed pattern.
See drawing, “Stand-by”.
- Select the PLAY mode.
Check the DOBM signal. See drawing “PLAY”.
|
LUI ULL LAL
POS. STAND-BY
2uS/DI¥
=
=
comes =
ms
=
=
POS. PLAY AUDIO INFORMATION euS/DI¥
MDA.00238
DRA 1
732-60?
CS 5 225 GB