Service manual

PV152 3-2 PROJO
CIRCUIT DESCRIPTION
supply is still operating at 1/2 voltage output, the Green
LEDs used for visual trouble sensing will reduce in inten-
sity, however they will remain lit. With the exception of
the SW+12V and SW+5V regulator. Which are turned off in
Stand By.
POWER SUPPLY FREQUENCY OF OPERATION DURING RUN:
When the Horizontal deflection is in operation, the power
supply frequency fluctuates in accordance to screen bright-
ness, causing differing demands for High Voltage replace-
ment. The normal operational range for the power supply is
between 80 KHz to 100 KHz. The lower the frequency, the
higher the current supplied to the load. During Stand-By,
it operates at 200KHz.
AC LOSS DETECTION:
AC is monitored by the AC Loss detection circuit. The AC
input from PQS1 pin (10) is rectified by DN09. This charges
up C009 and through DN08 it charges C008. When AC is
first applied, C008 charges slightly be-hind C009 prevent-
ing activation of Q001. If AC is lost, C009 discharges rap-
idly pulling the base of Q001 low, however DN08 blocks
C008 from discharging and the emitter of Q001 is held
high. This action turns on Q001 and produces a high. This
high is routed through D029 to the base of Q022 turning
it ON. The collector goes low and pulls the base of Q023
low turning it ON. The emitter of Q023 is connected to
STBY +11V, so when it turns ON, its collector output goes
HIGH. This high is now called V Mute 1.
SW+9V AND SW+5V REGULATOR OPERATION IN STAND-BY:
Both of these ICs as well as the STBY+11V and the STBY+7V
regulators are DC to DC converters just like last year. This is
because of the wide range of input voltages from Stand-By
to Normal operation of the Power Supply. The SW+12V regu-
lator (I908) and the SW+5V regulator (I907) are shut off
during Stand-By mode. This is accomplished by Q002 and
Q903. When the High for the power On/Off pin (53) of the
Microprocessor is inverted by the relay driver Q002, and
routed through the PQS1 connector pin (8). It is detected
by Q903, it’s collector will go low. This will pull pin (5) of
I907 and I908 low, turning off the two DC to DC convert-
ers.
SHUT DOWN CIRCUIT:
Shut down occurs when the shutdown SCR Q905 is acti-
vated by gate voltage. When Q905 receives gate voltage of
0.6V, the SCR fires and give a ground path for the emitter
of the LED inside I903. The light produced by turning on
this LED turns on the internal photo receiver and gener-
ates a high out of pin (3). This high is routed to the gate
of Q901 turning it on. This grounds pin (4) of I901 re-
moving Vcc and the power supply stops working. The rea-
son for the photo sensor I903 is to isolate hot and cold
ground.
SOME SHUT-DOWN DETECTION CIRCUITS SHUT OFF DUR-
ING STAND-BY:
During Stand-By, all of the secondary voltages are reduced
to approximately 50% of their normal voltage, except the
STBY voltages. This could cause a potential problem with
the Short Detection circuits for shutdown. To avoid acci-
dental shut down, Q903 also controls the activity of Q908
and Q909. During Stand-By, Q903 is turned On. This allows
the Base of Q908 to be pulled through D945. This action
turns off Q908. When Q908 is off, it doesn’t supply emitter
voltage to the collector of Q909. The base of Q909 is con-
nected to 6 Low Detection in-puts. When the power sup-
ply operates at 50%, the Short Detection circuit could
activate. By turning off Q909, no accidental shut down
operation can occur.
SUB POWER SUPPLY VISUAL LEDs:
ZP94 & 95 Chassis has 5 Green and 1 Red LED on Sub Power
Supply PWB. This chassis utilizes 5 Green LED’s in the power
supply cold side and a Red LED in the HOT side. The power
supply operates it two different modes, Standby and in
Projection On mode.
TURNING ON THE DEFLECTION POWER SUPPLY
When the Projection Television is turned on, the Micro-
processor outputs a high for Pin (35) which is inverted by
Q002. This low is routed through the connector PQS1 pin
(8) on the signal PWB to the Sub Power Supply PWB. It is
then routed to Q903, its collector will go High. This will
pull up pin (5) of I907 and I908, turning ON the two DC to
DC converters. The output of both DC to DC converters
I907 and I908, are used by the relay which supplies AC
voltage to the Deflection Power Supply on the Power/De-
flection PWB. The output of I907 SW+5V regulator sup-
plies B+ for pin (3) of the relay S901. The output of I908
SW+12V drives the base of Q911 turning it On and ground-
ing pin (4) of the relay S901. The relay now provides AC to
the bridge rectifier on the Deflection Power Supply.
HORIZONTAL B+ ON AND OFF CIRCUIT:
When the power supply goes into Stand-By mode (TV Off),
the Horizontal Drive signal for deflection is shut off This
is accomplished by Q002 and QP04. The Low out produced
from the Power On/Off pin 53 of the Microprocessor routed
through Q002 located on the Signal PWB. This Low is sent
through the PQS1 connector pin (8) to the Sub Power
Supply PWB and then through PQD2 connector pin (1) and
sent to the Deflection PWB. This Low is detected by the
base of QP04 turning it ON and the SBY +11V connected to
it’s emitter is made available at its collector. The collector
is connected to the Deflection B+ pin (22) of the Horizon-
tal and Vertical Drive IC, I701 via pin (8). This action stop
I701 from producing a horizontal deflection drive signal.