Service manual

CB-29
Audio Development
The +22VSB is supplied to pin 10. Pins 4, 9, and 12 are grounds for the amp. Pins 5 and 2 input left and
right (L/R) channel audio fed through C851 and C861, which eliminate any DC accompanying the signal.
Pin 3 provides a reference voltage. L/R output comes from pins 7 and 11. Pin 8 is a line that, upon receiv-
ing a switching DC level from the micro, mutes the speakers. This occurs when the user selects the speaker
cutoff option.
External Audio Output
External variable monitor output jacks are included on the CB jack-pack. Their signal is provided by
IC803, a dual op-amp that receives L/R from IC1400 into pins 3 and 5. This amp IC is powered by the
±14AUD at pins 8 and 4. Audio output to the variable audio output jacks comes from pins 1 and 7. The
op-amp provides a net gain of 12 dB.
1
2
5
6
4912
11310
87
OUTR
OUTL
VCC
GND
VREF
-INR
+INR
-INL
+INL
MUTE
GND
GND
IC804
1
2
3
4
C854
C864
C853
C863
R853
R863
C852
R859
R858
R870
C847
PROV
Mute
C862
+22VSB
CX841C842
C843
R868
R869
R861M R851M
R862M R852M
6
7
C861
C851
C865M C855M
C822
C832
1
2
3
45
6
7
8
IC803
R826M R836M
+14AUD
-14AUD
C850
C844M
C857
C856M
R823M
R833M
R822M
C823
R832M
R824M
C833
R834M
R825
R835
L&ROut
from Pins
6 & 7, IC1400
9S4
27 2625
Part of J1,
Jack Pack
Variable
Monitor
Out-Right
Variable
Monitor
Out-Left
To TV
Speakers
<<Figure CB-29>>