Service manual

CB-17
Video Processing
limiter threshold (1.5 mA for 27, otherwise 1.6 mA), the corresponding voltage across C2204 triggers the
limiter circuitry internal to IC2200, thus reducing output level (and therefore the contrast and brightness) of
the RGB signal. ABL helps to prevent blooming in the sweep that would otherwise occur as high current
draw lowers the sweep voltage. It also serves to extend the life of the picture tube.
<<Figure CB-15>>
Another factor involved in determining the RGB outputs is the AKB (automatic kine bias) circuit which
feeds into IC2200s pin 21. This signal is derived from the CRT circuitry. It uses feedback information
developed by three scan lines of video, one per color, in the over-scanned area above the video image. The
DC level returned is compared with an internal reference voltage that is determined in the service menu
settings for optimum black levels. RGB color is adjusted accordingly and finally output on pins 22 through
24 of the video IC.
IC Location Part # Notes
IC2200 221-01394 All Models
<<Table CB-5>>
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
R2252M
C2231M
C2232M
C2230
C2234
C2233M
C2235M
C2236M C2237
L2202
C2239
C2238M
R2253M
CRY2201
C2240M
R2256
R2254M
R2255M
Q2208
+9VSWF
R2282
PROV
R2281
PROV
C2240C2241
L2201
+9VSWF
R2251
R2250
C2228M
PROV
C2229M
PROV
C2225M
C2224M
C2223M
R2271M
R2242
D2211 D2212 D2213
C2222M
C2220M
C2219M
R2261M PROV
R2262M
PROV
R2263M
PROV
R2266M
PROV
R2265M
PROV
R2264M
PROV
C2245
R2280M
+9VSWF
R2287
PROV
Q2211
R2279M
R2278M
C2208M
C2209M
C2210M
R2206M
C2201
C2248M
C2247M
L2204
R2286M
PROV
R2285
R2283 C2249M
L2203
R2284M
C2250
C2204
+15VSW
B+
R2204M
R2213R2202
C2206
R2216
PROV
R2212
R2201
Q2210
PROV
R2205
PROV
R2267M
PROV
R2269M
PROV
R2268M PROV
C2244
PROV
R2203M
C2216M
C2217
ABL
Luma-Main
Chroma-Main
FSC
CB-In
CR-In
YUV-In
YUV-Switch
SDA
SCL
R-OSD+GEM
G-OSD+GEM
B-OSD+GEM
PiP-Brightness
FB-OSD+GEM
FB-PiP
B-PiP
G-PiP
R-PiP
Pins 21-24
Refer to RGB
Output Ckt
IQB32B44W
IQB36B44W
IQB27B44W
ONLY
IQB27B42W IQB32B86R
IQB32B42W IQB36B42W
IQB32B84R IQB36B86R
ONLY
Hand
Inserted
Component