Sony KDP-51WS550 Training Manual page 24

Vertical and IK-Prot 1 Protection Circuits
A BOARD
AC RELAY
RY6501
CN2003
35
35
CN0002
HA BOARD
STBY
8 8
5V
FIGURE 4-3 - AX-1 VERTICAL AND FBT OCP PROTECTION CIRCUITS
FBT Over Current Protection Circuit (IK Prot. 1)
(Reference Figure 4-3)
The secondary current in FBT is monitored by Q8008 at FBT/pin 1 (ABL). The +135V is used as the reference
voltage through the resistor voltage divider consisting of R8040, R8039, R8038, R8037, R8043, R8036 and
R8035. The combined voltage drop across R8036 and R8035 is used to turn off Q8008 and trigger the protection
circuit. In normal operation 0.6V is applied to the base of Q8008, turning it ON and a Low is present at the
collector. A High at the collector is needed to activate the protection mode.
As the current in the FBT secondary increases, the ABL line will pull more and more current through the resistor
network of R8035, R8041 and R8082. The voltage drop across R8035 will decrease, causing the combined
voltage drop across R8036 and R8035 to decrease. At the same time, the 0.6V at the base of Q8008 is decreasing,
which turns OFF Q8008. A High will be developed at the collector through pull-up resistor R8024 and Zener
diode D8019 (5.1V) will conduct. D8007 is now forward biased and a High is applied to IC0401/pin57 (H-Prot),
which will blank the video. The unit shuts down by IC0401/pin52 communicating with IC0002/pin31 (PF Micro);
IC0002/pin4 then communicates with IC0001/pin31 (Main Micro), which turns OFF the AC-Relay.
The unit video is muted, the AC relay shuts down and the Stby/Timer LED flashes a 7X sequence.
MA BOARD
IO-SDAT
31
IC0002
PF MICRO
4
D8007
31
D8019
69
IC0001
MAIN MICRO
48
D BOARD
IC0401
SDA
52
CRT DRIVE
H-PROT.
57
CN0001
15
15 CN2005
A BOARD
8
8
+135V
12V
R8040
R8039
R8024
5V
R8038
+
C8015
R8037
Q8008
R8043
0.6V
R8031 R8036
+
C8018 R8035
(FBT OCP)
22
4. AX-1 Protection Circuits
V-PROT.
56
14
14
CN2006
FEEDBACK
7
7
CN5004 CN5015/PIN 3
Q5101
+
C5103
FROM
R8041
FBT/
PIN 1
(ABL)
Q5103
BUFFER
D5110
4.7V
R5110
3
FB PLS
IC5101
V-DRIVE
V-DY (-)
9V
R5101
Q5102
15V
R5106
(VERTICAL
DEFLECTION
PROTECTION)
TVP16.4-3 1/14/04