Service manual

CA-2
CA CIRCUIT DESCRIPTIONS
<<Figure CA-2>>
Another winding from the chopper (pins 13 and 16) provides feedback to the regulation loop in ICX3400.
The AC from this winding is half-wave rectified by DX3408 to supply a negative voltage to pin 1 of the
regulator IC. ICX3400 is designed in such a way that it will adjust both its oscillating frequency and duty
cycle to maintain -41 volts DC on pin 1. Thus as changing power demands are reflected in the chopper
transformer, feedback to ICX3400 triggers a corresponding change in the regulated supply.
ICX3400
TX3401
QX3401
CX3410
RX3406
DX3406
CX3409CX3408
RX3404
RX3408RX3407
RX3403
B+ VDC
CX3411
DX3407
CX3412
CX3413
RX3409
DX3408
C3418
CX3416
LX3410
B+ VDC
RX3405
CX3415
RX3410
PROV
C3414
PROV
RX3411
PROV
DX3409
PROV
B+ VDC
16
To
Regulated
B+
To
+18 VSB
5
7
8
4
1
15
13
11
18
5
4
3
2
1
Q-Switching
Q-Reg
Q-Limiter
DZReg
R-Shunt
R-Bias
R-Div2
R-Div1
5
4
3
2
1
R-AntiSat
223-00028
ICX3400
<<Figure CA-3>>
QX3401 serves as the Over-Current Protection (OCP) switch. If the current sensing resistor, RX3403,
passes too much current to pin 4 of ICX3400 (the emitter of the internal switching transistor), the resulting