Power Supply - Philips PTV400 series Service Manual

set,
the coml.,vsite video is routed from the Jack Panel to the Multi-PIP
Module. ReModulated Video (RMV) is returned from the Multi-PIP
Module to the Jack Panel and then is applied to the S-VHS Switch IC,
IC670. External Video input from an External Video source can be
applied through the Jack Panel to the Multi-PIP Module on the
External Video line. Control of the Multi-PIP Module is via the 12C Bus.
The combed Chrominance signal is sent from the CCD Comb Filter
Module through the S-VHS Switch IC before being applied to the
NTSC Signal Processor, IC600. The combed Luminance is applied to
IC600. The S-VHS Switch IC selects either the tuner signal or the
Super VHS signals from the Jack Panel. The RGB and Fast Blanking
signals from the Character Generator IC, IC308, are applied to the
NTSC Signal Processing IC, IC600. These signals are matrixed when
On-Screen Graphics are needed and the product is output via RGB
lines to the Green CRT Board. Without RGB input from IC308, normal
program material is presented to the Green CRT Board. Both the Red
and Blue video information go through the Green CRT Board before
going to their respective boards.
The Luminance 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.
PTV Power Supply Module
The PTV Power Supply Block Diagram is shown in Figure 8. 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 MOSFET 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 R416 to
IC401-16. As the Standby Power Supply comes up to full operation,
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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 connected
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 a 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 transistor side
of the Opto-lsolator 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 Regulator,
Q401. Regulation is accomplished by monitoring the 130V Source via
a voltage divider network. This feedback reference voltage is sent
through the Control IC and the Output Voltage Regulator Opto-lsolator
to the Dual Controller IC. The 130V Source can be adjusted by
changing the reference voltage via the 130V Adjust potentiometer in
the divider network.
Cable connections and voltage check points for the Power Supply are
shown in Figure 9. To assist in making connections, plugs and jacks
have been color coded in the 1992 Projection Television. Note, jack
402 has a yellow plug and jack 404 has a red plug. Another feature is
that all boards have been coded with a letter. The Signal/Deflection
board is the "A" Board and the Power Supply board is the "P" Board
(see Figure 16). The 404 cable end that connects to the "A" Board is
labeled "A404" and the other end of the cable that connects to the "P"
Board is labeled "P404". This labeling method will help prevent
incorrect connections.
All voltages from the Power Supply can be checked at the jacks of
either the "P" Board or the "A" Board. Also shown in Figure 9 are the
Scan Derived voltages.
Shutdown Circuitry
The High Voltage circuitry, even though it is located on the main
chassis PCB, is separate from the Horizontal circuitry (Figure 10). The
High Voltage is phase locked to the Horizontal signal via the "Horiz
Pulse" as input through Q900. This pulse is applied to IC900-3, the
High Voltage Sync Processor. Its output drives the High Voltage
stages to the HV Output Transformer, T900. Here, the High Voltage
and Focus/Screen Voltage is developed. A Shutdown/Phase Sense
winding from T900 develops the signal used for phase correction
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