Sony KDP-51WS550 Training Manual page 25

Vertical Deflection Protection (V-Prot)
(Reference Figure 4-3)
The operation of the vertical deflection circuit is monitored using the vertical feedback signal from the VDY
(CN5015/pin3) and the feedback pulse developed at IC5004/pin 3 (vertical drive IC). When the vertical circuit is
working properly, the vertical feedback signal is fed direct to the Y/C CRT Drive IC0401/pin56 through R0426,
and the feedback pulse is generated at Vertical Drive IC5101/pin3.
If the vertical drive signal IC5101/pin5 (not shown) to the VDY stops due to a defect, the feedback signal (CN5015/
pin3) and feedback pulse (IC5101/pin3) will also stop, and the unit will go into vertical shut down.
The feedback pulse circuit applies a hard ground to IC0401/pin56 to ensure that the unit goes into vertical
shutdown if a defect occurs in the vertical drive circuit. The vertical feedback pulse is amplitude limited using
D5110 (4.7V Zener diode). The pulse passes through buffer Q5103 and is applied to the base of Q5102, turning
it ON, while applying a Low to the base of Q5101, turning it OFF. With Q5010 OFF, the V-DY feedback will be
applied to IC0401/pin 56, indicating proper vertical deflection operation.
If the Vertical deflection should cease due to a defect, the feedback pulse at IC5101/pin 3 will not be developed
(no pulse through Q5103 buffer), Q5102 will turn OFF and Q5101 will turn ON. The V-DY feedback signal will go
to ground. IC0401/pin 56 detects the missing V-DY feedback signal and places the unit in vertical shut down.
In vertical shut down mode, only the video is muted, the AC power and Audio remain ON and the Stby/
Timer LED flashes a 4X sequence.
HV LVP (Low Voltage Protect) Circuit
RV8002
HV LVP
R8017
TO HV
CONVERTER R8014
(IC8002)
FEEDBACK
R8015
SIGNAL
RY6000
AC RELAY
CN0001
13
13
CN2005
CN2006
4
4
CN5004
6.5V
R8033
R8025
FIGURE 4-4 - AX-1 HV LOW VOLTAGE PROTECTION CIRCUIT
MAIN MICRO
69
IC0001
HV-PROT.
52
A BOARD
IC8004
-
7
+
-
0V
7
+
23
4. AX-1 Protection Circuits
MA BOARD
13
6
FBT
T8001
6.5V
5
2.45V
2
2.2V
3
D BOARD
R8028
9V
TVP16.4-4 1/30/04