JVC 250 service manual LVPS - Operation

Chapter 3---Electrical

Figure 3-1Low Voltage Power Supply I/O Diagram.

LVPS - Operation:

AC power is delivered to the Low Voltage Power Supply from the AC line filter. The AC is rectified to a DC Voltage, filtered, and goes through a power factor correction circuit to force the current waveform to follow the voltage waveform.

The +5.1V Standby is on whenever AC power is connected to the projector and the circuit breaker on the rear panel is in the ON position. When the AC Circuit Breaker is in the ON position, the LVPS supplies the +5.1 V to the System Controller PCB. The System Controller PCB drives the /FAN_ENA signal to the LVPS to turn on the +24V Standby power for the cooling fans. If the System Controller PCB does not receive a POWER ON command from an IR remote control or a PC, it waits about 10 minutes and then tells the LVPS (/FAN_ENA goes high) to shut off +24V Standby power. This shuts off the cooling fans. More importantly, after the System Controller PCB receives a POWER OFF command it waits 10 minutes, and then tells the LVPS to shut off the cooling fans. This gives the Arc Lamp and the PCBs time to cool down to avoid damage or reduction of operating life.

When the projector receives a POWER ON command from an IR Remote Control or PC, the System Controller PCB sends the /LV_ENA signal to the LVPS. The Low Voltage Power Supply needs to receive the /LV_ENA from the System Controller PCB and the /COVER_ON signal to activate all the non-standby voltages. These include:

3-4 Model 250 Service Manual