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The composite
video signal from the Switch IC is also applied to
the NTSC Signal Processor
to develop
sync for the Vertical and
Horizontal
Oscillators.
The horizontal
drive signal is applied to
the Horizontal
Circuitry
where
the scan-derived
voltages
are
developed.
The Horizontal
Pulse (H Pulse) is sent to the High
Voltage
Sync Processor,
IC900, which drives the High Voltage
Output
Circuit.
This circuit develops
the High Voltage,
Screen
(G2)
Voltage,
and Focus
Voltage.
The vertical
signal
exits
IC600 and is applied
to the Vertical
Deflection
IC, IC550.
The
amplified
vertical
signal drives the vertical windings
of the Yoke.
The
Horizontal
and
Vertical
signals
are monitored
by the
Shutdown
Circuitry
which will stop High Voltage
development
if
either signal is missing.
PTV Power Supply
Module
The PTV Power
Supply
Block Diagram
is shown
in Figure
9.
The 120Vac Source
is applied to a Bridge Rectifier
circuit, which
produces
approximately
155Vdc
for the Switching
Mode Power
Supply.
There are two separate
Switching
Mode Power Supply
circuits
used in the PTV. The 155V is supplied
to both of these
circuits.
Each circuit has its own transformer
and Power MOS-
FET regulator.
Both regulator
circuits
are controlled
by one
Controller
IC, IC401.
One of the circuits
is used for Standby
operation,
with both circuits being used for Full Power operation.
As soon as the TV Set is plugged
into an AC Receptacle,
the
Standby
Power
Supply
starts running from the voltage
applied
through
R415
to IC401-16.
As the Standby
Power
Supply
comes
up to full operation,
approximately
12Vdc is provided
via
Diode
D405
to the Controller
IC for the continuing
Source
Voltage.
A 15V-Standby
Source
is used as the source
for the
5V Regulator,
IC408.
The Standby
Power Supply runs all the time the chassis
is con-
nected
to the AC Power
Source.
A square-wave
signal
exits
IC401-7
to drive
the Standby
Regulator,
Q402.
Q402
is a
Power
MOSFET
device
that drives
the Standby
Transformer,
T402.
The SMPS is switched
to full-power
by logic level control
from the Microcomputer.
This logic level is input to the Control
IC, IC402-16.
The Control IC operates
the On/Off Opto-lsolator,
IC406.
During
Full Power
On, the transister
side of the Opto-
Isolator
effectively
opens
and IC405
is allowed
to control
the
regulation
of the Full Power
Supply
via IC401.
A rectangular
wave signal
is then allowed
to exit IC401-10
to the Full Power
6
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