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