BOSE OC-1 Schematic
Product:
OC-1 AWCS II Option Card
Part Number:
174786-B1
Subject:
Symptom: A clicking sound is heard when there is no signal or a low level signal.
Reason: The OC-1 card does not stay in a mute state when the signal drops below the mute
threshold. The clicking sound is heard as the unit quickly mutes and unmutes.
Solution: Modify the OC-1 card to increase the mute time by adding a 10k Ohm, 1/4W resistor
in series with D5. Refer to the figures below and to the OC-1 AWCS II Option Card service
manual part number 174786.
A clicking sound is heard.
D5
10k
100
R8
6
5
-
+
R10
200K
C57
3.3n
R9
200K
U1
1/2
RC4559
7
R93
10.0K
D5
1N4148
Added
Resistor
C7
10
10K
+15V
R12
200K
R111MR13
10.0K
C10
22
3
U2
+
2
-
1/2
1
RC4559
1
U1
C4
D4
R4
R2R1R3
FRACAS 297
Date Issued: 3/2001
C3
D1
D5
J1
C10 U7
1
1
C7
U3
U2
D6
1
C11
C17
C16
C41
C51
C49
C27
C28
U4
1
C13
C15
C45
J5
C50
C44
C53 C55
1
C52 C54
C56
1
C46
C47
C48
C40 C43
C36
C37
C42
C32
U5
C35
C34
C30
J4
C29
C31C33
C20
C21
C22
OC-1
U6
1
1
OC-1 Card PCB
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