P Board
P Board
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Main Power Board
Main Power Board
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When AC is applied to the TV, the Standby circuit of the P board outputs 5Vdc to the AP board. The STB5V
passes through the AP board and enters the A board. On the A board The STB5V is converted to 3.3V to power the system
control circuit for standby operation. The STB3.3V is also applied to the Remote Control receiver and the power LED on the
V board. The MPU (IC1100) of the A board outputs the SUB_ON command to provide a ground connection to relay RL802
of the power supply board. On the AP board, the SUB_ON command is used to turn on a circuit (not shown in the diagram)
that provides STB5V to relay RL802 via pin 15 of connector AP2/P2. When the relay is closed, DC voltage from the rectifier,
approximately 105Vdc, is supplied to the LCD panel for conversion into 24Vdc. The output of the 24V generator passes
through the P board and enters the AP board for conversion into SUB_5V, DTV9V (SUB_9V), and HQ3.3V.
If the power button (main unit or remote control) is not pressed within 25 seconds after applying AC to the unit,
the SUB_ON command goes low to disengage the power relay. When the power button is pressed, the SUB_ON command
goes high to repeat the same operation. The voltages remain present until the unit is turned off.
When the unit is turned on, the LCD panel’s inverter circuit uses the 24Vdc source to generate the 120Vac to
illuminate the CCFLTs. The INV_ON command and the 12Vdc source enter the panel’s drive circuit via the connector
AP2/P2 and P5 of the P board. The inverter circuit is monitored for abnormality. When a defect is detected, a SOS (High)
output is provided to the A board MPU (IC1100) via Connectors P5 and P2/AP2.
Caution: The P board is not to be repaired by you. It is to be exchanged only.
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