Service manual

CB-20
CB CIRCUIT DESCRIPTIONS
C5101 causes the G1 to become more positive. Since G1 is otherwise considered ground for the CRT, this
action reduces any remaining CRT potential, thus eliminating afterglow. C5101 controls the rise time of this
circuit, while C5106 controls the dead-time on response.
Deflection Processing
IC2200 also supplies deflection signals to drive the sweep section. Vertical drive is supplied in the form of
positive and negative ramp signals on pins 13 and 14 respectively. Simultaneously, a vertical ramp is also
supplied from pin 5 of the video processor. This vertical signal is converted into vertical sync, directly by
the PiP board, and through transistors Q6002 and 6004, which then provide the v-sync to the microproces-
sor and the Gemstar
®
board.
<<Figure CB-18>>
Horizontal drive comes from pin 19 of IC2200. This signal drives the horizontal output transistor (HOT).
The flyback line taps off of the HOT collector to provide feedback to pin 18 of the video processor.
Furthermore, this same flyback signal provides horizontal sync for the PiP, Gemstar
®
, and, through Q6001,
the microprocessor. Pin 18 of IC2200 also serves the second purpose of protecting the set from high
voltage. While pin 18 normally receives horizontal feedback signal, a high voltage situation will activate
QX3001. The collector of this transistor will then attenuate that signal. If attenuation lowers the signal to
1.0 Vp-p or below, IC2200 will shutdown the CB receiver. Lastly, in terms of horizontal deflection, pin 11
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24 25
36
26
27
28
29
30
31
32
33
34
35
37
38
39
40
41
42
43
44
45
46
47
48
APED
C1IN
ABLIN
CVBS1/YIN
VTIM
MONOUT
NC
XTAL
FSCOUT
APCFIL
VCC2
TV/C2IN
COMB-CIN
YCLAMP
COMB-YIN
GND1
EW
REF EYIN
ER-YIN
EB-YIN
GND2
CVBS2/Y2IN
ABLFIL
VDP
VDN
VMOUT
REG
SCP
HP/XRAYPROT
YUV-SW
SDA
SCL
VCC1
R2IN
G2IN
HD-OUT
AFCFIL
IKIN
ROUT
GOUT
BOUT YS1
B1IN
G1IN
R1IN
YS2/YM
B2IN
IC2200
C2240C2241
L2201
+9VSWF
R2214M
R2215M
C2213
Q2203
+9VSWF
C2212M
R2219M
R2220M
R2218
1
2
C2252M
PROV
R2225M
+9VSWF
R2226M
H-Drive
VDN
VDP
E/W
V-Ramp
Pin 18: Refer to
HV Shutdown Ckt
PROVISIONAL ON
IQB32B44W
IQB36B44W
ONLY
4X9