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CIRCUIT DESCRIPTION
Three primary voltages are developed that are needed to sustain run, maintain regulation, and support the
Shutdown Circuitry. They are Run Voltage generated from pin (8 and 9) of T901, +28V used for regulation,
and STBY +11V, respectively. The STBY represents always on; designating a supply that is active
when the unit is connected to AC power. The Power Supply utilizes a Shutdown circuit that can trigger
Q905 from 16 input sources. (6 of these are not operational in Stand by mode). I903 is activated by Q905,
applying gate voltage to Q901, which grounds out the Vcc at pin (4) of I901, disabling the power supply.
Audio Front 29V Regulator SW+29V Indicated by D912
The Audio Front 29V supply is generated from pin (17) of T901. This output is protected by E992, recti-
fied by D910 and filtered by C918. This supply is routed to the Rear Audio Output IC IC01. This voltage is
what illuminates the Green Visual Trouble Shooting LED, D912.
Audio Rear and Center 29V Regulator SW+29V Indicated by D913
The Audio 29V supply is generated from pin (16) of T901. This output is protected by E993, rectified by
D911 and filtered by C917. This supply is routed to the Rear Audio Output IC IS16 and Center Audio
Output IC IC15. This voltage is what illuminates the Green Visual Trouble Shooting LED, D913.
STBY+11V Regulator I906 Indicated by D949
The STBY+11V supply is generated from pin (11) of T901. This output is rectified by D918 and filtered by
C928. This supply is routed to the Stand By +11 Regulator I906 pin (1). This voltage is what illuminates the
Green Visual Trouble Shooting LED, D949. The use of the power supply creating the SBY+11V supply
eliminates the need for a Stand-By transformer. The following explanation will describe the Turning ON and
OFF of the projection television.
STBY+7V Regulator I905 Indicated by D927
The STBY+7V supply is generated from pin (11) of T901. This output is rectified by D918 and filtered by
C928. This supply is routed to the Stand By +7 Regulator I905 pin (1). This voltage is what illuminates the
Green Visual Trouble Shooting LED, D927.
Power Supply Frequency of Operation during Run
The sub power supply in the ZP94/95 chassis works very similar to the previous models. This power supply
runs at 50% efficiency when the AC is applied with the set OFF. When the Horizontal deflection is in
operation, the power supply frequency fluctuates in accordance to current demands. 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.
Power Supply Operational Frequency during Stand-By:
When the Horizontal deflection is defeated, the power supply no longer has a deflection load. The three
resistors connected to the source of the internal Switch MOSFET inside I901 via pin (2) detect this low
current demand. Pin (1) of I901 is the over current detection pin, however it is also the current demand-
sensing pin. When the current demand is low due to horizontal defeat, pin (1) will be less than 1.4V and the
internal frequency will switch to 200Khz. This is caused by the Quasi Resonant circuit operation. This
reduction of power supply frequency will move the frequency above the Bell of the power supply trans-
former and all secondary voltages will reduce to approximately 1/2 of their normal voltage. Due to the fact
that the power supply is still operating at 1/2 voltage output, the Green LEDs used for visual trouble sensing
will reduce in intensity, however they will remain lit, with the exception of the SW+12V and SW+5V
regulator. Which are turned off in Stand By.