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B+ GENERATION FOR SUB POWER SUPPLY DRIVER
Vcc for the Driver IC is first generated by the AC input.
This voltage is called Start Up Voltage. I901 requires
16V DC to operate normally. It will begin operation at
6.8V DC on pin (4) of I901.
When AC is applied, AC is routed through the main fuse
F901 (a 6 Amp fuse), then through Line filters L901,
and L902 to prevent any internal high frequency radia-
tion back into the AC power line. After passing the fil-
ters it arrives at the main full wave bridge rectifier D901
where it is converted to 150V DC voltage to be supplied
to the power supply switching transformer T901 pin (1).
One leg of the AC is routed to a half wave rectifier D906
where it is rectified, routed through R903 and R904
(22K ohm resistors), filtered by C910, clamped by a 30V
Zener D902 and made available to pin (4) of I901 as
start up voltage. When this voltage reaches 6.8Vdc, the
internal Regulator of I901 is turned On and begins the
operation of I901.
When the power supply begins to operate by turning on
and off the internal Switch MOS FET, the 150V DC routed
through T901, in on pin 1 (Drain) and out on pin 2
which is the Source. The Source of the internal Switch
MOS FET is routed out of pin (2) through three low ohm
resistors to hot ground. When the internal Switch MOS
FET turns on, it causes the transformer to saturate, build-
ing up the magnet field. When the internal Switch MOS
FET turns off, the magnet field collapses and the EMF is
coupled over to the secondary windings, as well as the
drive windings. The drive windings at pin (5) produce
a run voltage pulse which is rectified by D903, filtered
by C909, then routed through R906, filtered again by
C908, clamped by D902, and now becomes run voltage
(16V) for I901.
DEFLECTION POWER SUPPLY VISUAL LEDS
The Chassis has 4 Green and 1 Red LEDs on the Deflec-
tion Power Supply PWB. This chassis utilizes 4 Green
LEDs in the power supply cold side and a Red LED in the
HOT side.
POWER ON MODE
When the Power is turned ON, the LEDs light;
1) DP06 Indicating Vcc applied to the Power Supply
Driver IC IP01 pin 4 (Colored RED)
2) DP23 Indicating 115V Deflection B+ is available
(Colored GREEN)
3) DP37 Indicating SW +5V B+ is available (Colored
GREEN)
4) DP11 Indicating SW +9V B+ is available (Colored
GREEN)
5) DP35 Indicating 28V B+ is available (Colored
GREEN)
PV154 - 923-03506
CIRCUIT DESCRIPTIONS
DEFLECTION POWER DRIVER B+ GENERATION
3-6
LED USAGE
The Visual LEDs are useful in Trouble Shooting. Without
removing the back cover, some diagnostics can be
made. By observing the operation of the Red and Green
LEDs, the technician can determine if the Deflection
Power Supply is running. By monitoring these LEDs at
turn on, one can determine if a line is loaded. If an
LED tries to light then goes off, or only lights dimly, a
loaded condition should be considered. Remember, this
power supply doesn't operate when the set is in
Standby. The following will examine each LED and how
they are lit.
DP06
Indicating Vcc applied to the Power Supply Driver IC
IP01 pin 4 (Colored RED). If B+ (Vcc) is present on
the Deflection Power Supply Driver IC? LED will be ON.
DP23
Indicating 115V Deflection B+ is available (Colored
GREEN). This LED is connected directly to the 115 V
deflection B+ line. If it's lit, 115V is available.
DP37
Indicating SW +5V B+ is available (Colored GREEN).
This LED is connected directly to the SW +5V B+ line.
If it's lit, +5V is available.
DP11
Indicating SW +9V B+ is available (Colored GREEN).
This LED is connected directly to the SW +9V B+ line.
If it's lit, +9V is available.
DP35
Indicating 28V B+ is available (Colored GREEN). This
LED is connected directly to the +28V B+ line. If it's
lit, +28V is available.
START UP VOLTAGE GENERATION
Vcc for the Driver IC is first generated by the AC input.
This voltage is called Start Up Voltage. IP01 requires
21V DC to operate normally. It will begin to regulate
at 14V DC on pin (4) of IP01.
When AC is applied by the relay on the Sub Power
Supply R901, AC is routed through the connector PQD1.
Then it arrives at the main full wave bridge rectifier
DP01 where it is converted to DC voltage. One leg of
the AC is routed through RP02 and RP03 (3.9K ohm
resistors), filtered by CP05, and made available to pin
(4) of IP01 as start up voltage. The Red LED DP03 is
illuminated by this power supply. When this voltage
reaches 6.8Vdc, the internal Regulator of IP01 is turned
On.
RUN VOLTAGE GENERATION
After the transformer TP91 is started, a pulse is output
from pin 8. This pulse is rectified by DP02, filtered by
ZP26/28 - SERVICING
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