Hitachi 51F510, Manual

Page: 10 / 152

DP-4X DEFLECTION SIDE SHUTDOWN DIAGRAM EXPLANATION
PAGE 01-04
See The DP-4X Deflection Side Shutdown Diagram for (A), (B), (C), (D).
HIGH VOLTAGE TOO HIGH DETECTION: One of the Shutdown circuits for output (A).
•
DH15 High Voltage Too High Sensing Circuit.
This circuit monitors the High Voltage line generated by rectifying the pulse from the flyback TH01 pin
7 . If the voltage created by rectifier DH13 and capacitor CH17 at the cathode of DH15 goes too high, this
zener will fire. This high will be routed to pin
8
of
PDS3 PROT_OVP (A)
to the
PROT_OVP and
PROT_OCP Shutdown Diagram .
•
At the same time, the zener diode DH14 will fire and this high will be routed to pin 7 of IH01 . This is the
Horizontal Drive for High Voltage and this IC will shut off, turning off High Voltage drive pulses.
•
The ABL is tied to the cathode of DH15 via RH32 . This resistor offers slight “Trigger Point” deviations
as the screen brightness fluctuates and caused the High Voltage to bounce. By tying ABL to the Excessive
High Voltage detection voltage, the firing point is slightly altered.
VERTICAL OUTPUT CIRCUIT EXCESSIVE CURRENT DETECTION: One of the Shutdown circuits for
output (A).
•
Q604 Vertical Circuit Excessive Current Sensing Circuit.
This circuit monitors the SW+28V line going to I601 Vertical Output IC. If the IC draws too much cur-
rent, R629 will develop a larger voltage drop. This will cause the base voltage of Q604 to fall turning on
this transistor. When this happens, its collector will go high. This high will be routed through
D608
and to
pin 8 of PDS3 PROT_OVP (A) to the PROT_OVP and PROT_OCP Shutdown Diagram .
-5V NEGATIVE VOLTAGE LOSS DETECTION: One of the Shutdown circuits for output (A).
•
DK18 –5V Loss Detection Circuit.
The purpose of the Negative Voltage Loss detection circuit is to compare the negative voltage with its
counter part positive voltage. If at any time, the negative voltage drops or disappears, the circuit will pro-
duce a Shutdown signal.
There are two resistors. One to the positive v5V
RK23 and one to the negative voltage –5V
RK22 . At their tie point, (neutral point) , the voltage is approximately (-1V). If however, the negative
voltage is lost, the neutral point will go positive. This in turn will create a Shutdown Signal through
DK18 . This high will be routed to pin 8 of PDS3 PROT_OVP (A) to the PROT_OVP and PROT_OCP
Shutdown Diagram
.
PROT_OVP INPUT INDICATED BY (C) One of several Shutdown outputs for item (A).
•
The
PROT_OVP
signal (Active High) is shown in the center left hand side of the diagram. This is an in-
put from the Deflection Power Supply Shutdown Circuit Diagram. There are 3 circuits from the Deflec-
tion Power Supply Shutdown Circuit Diagram that provide inputs to this diagram.
•
This is explained on Page 01-06.
SW +10.5V SHORT DETECT INDICATED BY (D) Shutdown output for item (B).
•
D723 is attached to the B+ SW +10.5V line which is generated on the Signal PWB by QY62 . If this volt-
age disappears or is shorted, D723 cathode will be pulled low generating a Low on Pin 9 of PDS3 and
output as a shutdown signal on the PROTECT_OCP indicated as item (B) .