Olympus OEP-3, Service Manual

Page: 130 / 176

4-22
OEP-3 V1 (UC)
(7) AGC (Automatic Gain Control) circuit
This unit mounts a peak AGC circuit that has actual results on the medical market.
The peak value of the RGB signal output from IC203 is sampled by Q304, Q305, and Q306. The
resultant signal is passed through a low-pass filter (R315 and C312) and then input to the operational
amplifier (IC302). The control level is properly adjusted by IC302. The input signal is then passed
through a switch (IC307) for manual gain adjustment (output signal at pin 3 of IC303) and input to the
control pin of GCA (Gain Control Amplifier)(IC304 to IC306).
Fig. 1-6 AGC Circuit
(8) EVR (electronic volume) adjustment circuit
Adjustment is partially performed using an electronic volume by IC303.
IC303 has a five-channel internal DA converter. The four channels of it are used for “VBS gain”,
“offset”, “AGC gain”, and “manual gain”, respectively. Adjustment is performed by I
2
CBUS.
(9) EEPROM
EEPROM (IC301) is mounted to store the setting and adjustment values of this board. This EEPROM
writes or reads data by I
2
CBUS.
R316
22k
R315
2.2k
C312
47uF
6.3V
C311
10uF
16V
R314
0
FL303
LPF
C318
47uF
6.3V
R327
1k
CL315
R319
1.8k
R322
1k
C329
0.1uF
Q303
XN4601-TW
Q306
XN2501-TX
R313
1.8k
R310
33
A+9V
C313
10uF
16V
R324
2.7k
R323
8.2k
C316
0.1uF
R325
10k
R329
470
R328
15k
IC302
LM358PSR
C326
0.1uF
CL317
D301
UDZ-TE-17-4.7B
R342
10k
C350
0.1uF
Q307
DTC124EKA-T146
IC307
TC4W53F(TE12R)
IC309
LM358PSR
C325
0.1uF
C332
47uF
6.3V
IC306
BA7655AF-E2
C321
0.1uF
R337
2.2k
I2
6
FG1
19
FG2
20
8
8
5
5
4
4
1
1
O3
9
O2
3
OUT
7
I1
12
O1
13
G4
10
G3
15
G2
16
G1
18
IN
2
5 2
4
6 1
3
4
3
2 1
5
6
IN-2
2
IN-1
5
IN+2
8
VCC 1
OUT1
7
OUT2
4
GND
3
IN+1
3
VEE
4
VSS
8
VDD
5
A
1
2
INH
7
6
6
IN-2
2
IN-1
5
IN+2
8
VCC
1
OUT1
7
OUT2
4
GND
3
IN+1
5
OUT2
6
CTL2
7
IN2
2
CTL1
8
VCC
4
GND
1
IN1
3
OUT1