Sony STR-DE845 Training Manual page 33

If a circuit failure disabled D912, error regulator IC902 would be operational, outputting a correction voltage of
about 0V to Switching regulator IC901/pin 1 in this oscillator burst (standby) mode. This 0Vdc is output because
IC901 is producing less power (outputting only bursts), but error regulator IC902 outputs 0V attempting to raise
the output to normal. Unfortunately, 0V is below the normal operating range of the oscillator in IC901 so IC901
would attempt oscillation a few times and finally shut off. If shutoff occurs, removing Vcc to IC901 will reset it.
Consequently, both of these two control voltages must be input for oscillator IC901 to function in the Standby
Mode. See Chart 9-3 below:
Switching Regulator input
IC901/pin 4 (Vcc)
IC901/pin 1 (Error correction) 1.1 Vdc
S901
62Vdc
R908
33k
1W
D904
N
R907
Q903
D903
18V
18V
R905
SOURCE
IC901/1 PC901/3 D912/A IC902/2
STBY 1.1V 9.5V
7.5V
2.2V
ON
Power Supply Operation – Power ON – P.Cont 1 comes from the CPU and is used to toggle the power supply
between the Standby Mode (LOW) and the Power ON Mode (HIGH). In the Power ON mode, the HIGH has two
purposes. The first is to apply full voltage to switching regulator IC901/pin 4 (20Vdc). See Figure 9-3. This
changes the oscillator output of IC901 from a burst signal to a continuous oscillator output.
Chart 9-3 - Standby Mode IC901 Control Voltages
Voltage
11 Vdc
F901
5A
TH901
9.1Ω
D902
24V
SOURCE
Q902
P
11V=STBY 20V=ON
+18V
Q901
4
P
R904
3
6.8V=ON
18V=STBY
0V 17V
13V
27V
FIGURE 9-3 - DAV- C700 POWER SUPPLY CIRCUIT
9. DAV-C700 Switching Type Power Supply
Vcc input for burst oscillator output
Fixed error correction voltage to prevent oscillator shutdown
T901
163V POWER
+ TRANS.
C902
3
C916
IC901
SW REG
4
STRF64265
1
5.6V
HEAT
R912
SINK
1
PC902
TLP421
ISOL.
3
2
PC901
ISOLATOR
TLP421
5.6V Vcc
24V
5
4
IC907
INV.
Q915
TE85R
2
31
Purpose
CN905
IC905
13V
REG
BA05
10
27V LINE
R919
CN904
R920
1
IC902
ERROR
2
SE-B2
3
R917
2
R916
4
D912
(15V)
Q905
Q908
STBY=0V
ON=4.7V
9.2aA124 1415
5.6V
TO CPU
IC901
4
(DVD BD.)
P CONT 1
(DVD BD.
1
CN008)
2
STBY=19V
ON=28V
CHASSIS
HOT
COLD
11/27/01