CIRCUIT DESCRIPTIONS
PV154 - 923-03506
3-7
ZP26/28 - SERVICING
CP05 and takes over as Run Voltage (16.3V) at pin 4
of IP01.
REGULATION
Figure 2 is a simplified diagram of the main Power
Supply used in some Projection Television chassis.
The primary control element of the power supply is
IP01 (the Switching Regulator IC), in conjunction with
transformer TP91. These two components, along with
the supporting circuitry, comprise a closed loop
regulation system.
Unlike previous Pulse Width Modulated (PWM) Switch
Mode power supplies, the regulation system in this
chassis utilizes Frequency Control Modulation with an
operational frequency of 60KHZ to 85KHZ,
corresponding to full load and no load conditions,
respectively. Primary regulation is provided by IP03,
IP02 and into IP01, regulating the switching frequency
at pin (3) of I901 via pin 1.
Two voltages are developed that are needed to sustain
run and maintain regulation:
1. Run Voltage generated from pin (8 and 9) of TP91
rectified by DP02 and supplies run voltage to IP01
pin (4).
2. 115V Deflection Voltage generated from pin (11)
of TP91, rectified by DP15 and used for regula-
tion and powering the Deflection and regulation
circuitry.
DEFLECTION GENERAL INFORMATION
The deflection circuit differs from conventional projec-
tion products. It utilizes, two horizontal output cir-
cuits. One for Deflection and one for High Voltage. There
are many terms around the Horizontal circuit that are
not shown on the Diagram. Some of these terms are:
CUT OFF
Cut off collapses the Vertical circuit during I
2
C Bus
alignments, during CRT Set Up.
ABL
ABL voltage is generated by monitoring the current
through the Flyback transformer. This voltage will
fluctuate down when the scene is bright and up when
the scene is dark. The ABL voltage will manipulate the
screen brightness and contrast to prevent blooming
under these conditions.
H BLK
Horizontal and Vertical Blanking is developed within
the Deflection circuit. The Horizontal Blanking pulse
operates around 13V P/P and is produced by taking a
sample pulse from the Deflection transformer T752.
V BLK
The Vertical Blanking pulse is generated from the
Vertical output IC, I601 pin (11). This pulse normally
operates at 21V P/P.
IR
The Infrared Pulses coming from the remote control
are routed through the Deflection PWB to the Digital
Convergence Unit. During DCAM (Digital Convergence
Adjustment Mode), the Remote Control provides
manipulation pulses for the DCU.
DIG RGB/ BUSY
This indicates Digital RGB and BUSY.
·
Digital RGB represents the On Screen Characters
produced by the DCU for generating the Digital
Convergence adjustment grid and text produced
during certain conditions such as HD Focus, Sen-
sor Initialization, Data Storage, etc…
·
Busy notifies the DAC1 (I006 pin 1) which in turn
notifies the Microprocessor I001 that the DCU has
entered the DCAM. During this time, the Micro-
processor ignores the remote control commands.
D SIZE
Digital Size is a control signal for raster enlargement
when HD FOCUS is operated. Raster enlargement is
required for the HD FOCUS PATTERN to hit the photo
sensors.
This signal is output from DCU and routed to the base
of Q710 for enlarging horizontal size through the Pin
Cushion circuit and through Q603 to the Vertical
Output IC I601 pin (4) to enlarge the vertical size.
In some cases, this control signal is called “A.SIZE”.
It’s the same function between DIG.SIZE and A.SIZE.
TO CONVERGENCE YOKES
The DCU provides compensation signal for deflection
abnormalities to the convergence output IC. The Con-
vergence output IC in turn, amplifies the signals and
routes them to the convergence yokes.
+B 115V1
The Deflection transformer receives the 115V V1 DC
source.
+B 115V2
The High Voltage Transformer TH01 (Flyback) receives
the 115V V2 DC source.
HV PARABOLA
See DF Out.
SCREEN 700V
700V Supplied to the screen grids on the CRTs.
FOCUS 12KV
Focus voltage supplied to the CRTs.
