Hf Path; Dc Settings - Philips CDR775 Service Manual

GB 62 8.
8.3.7

HF Path

Description
The pre-amplified HF-signal is presented to both n=1 and n=2
amplifier circuits. The mux/demux switches via software and
micro processor controlled S1 and S2 lines between either one
of the amplified n=1 or n=2 signals. The signal will then follow
n-dependant filtering
n=1 AMP
3173
430R
2
n=2 AMP
PRE AMP
HF
3191
430R

DC Settings

Set the power and reset connections as described above in
"1.1.1. Supply Voltages". Check the following voltages :
Force Pin
Emitter
S1 and S2 "HIGH" Collector
S1 and S2 "LOW" Collector
S1 and S2 "HIGH" 13
S1 and S2 "LOW" 13
S1 and S2 "HIGH" 3
S1 and S2 "LOW" 3
Figure 8-29
CDR775 Faultfinding Guide
+5VHF
HFGND
HFGND
3174
7023
BFS20
430R
HFGND
2143
390p
330p
2149
680p
HFGND
+5VHF
HF
3192
7009
BFS20
430R
HF
HFGND
2164
180p
HFGND
Location Measure
2.4 ± 10%
7006
1.9 ± 10%
7010
1.9 ± 10%
7010
1.6 ± 10%
7025
1.6 ± 10%
7025
3.2 ± 10%
7025
3.2 ± 10%
7025
CL96532086_058.eps
another amplification and filtering circuit. The filtering again is
controlled by the S1 and S2 lines, dependant on whether the
disc starts up (speed n=1, S1 and S2 Low), disc plays at speed
n=1 (S1 Low, S2 High) or disc plays at speed n=2 (S1 and S2
High).
DUAL 4 CHANNEL
MUX/DEMUX
+5VHF 7025
74HCT4052D
2130
10
16
VCC 0
0
100n 4x 9
7
3
VEE 1
6
8
GND G4
HFGND 1
0
5 HFGND
1
3
2
2
HF
4
3
2141
12
2n2 14
13
2146
15
1n5 11
9
+5VHF
HF
HFGND HFGND
1K
3196
BC858B
7007
7010
BC848B
HFGND
HFGND
Figure 8-28
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3
S1
S2
HFGND HFGND
HFIN
2142 F309
2145
22n
F156
3178
HFGND F310
47p
1K 3181
2150
22K
F159
47n
HFGND
7000
SAA7324
1 HFREF
2
HFIN
3 ISLICE
FRONT
4
VSSA1
END
5 VDDA1
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