JVC 340 SC, 330, 370 SC service manual System Power Supply

Chapter 2—Functional Descriptions

The Raster Timing Generator provides timing signals to the System Controller Board, selects the appropriate incoming sync signal and produces the timing signals for controlling the geometry of the raster.

The Vertical and Horizontal Deflection Boards produce their respective sweep currents to drive the deflection yokes. The Vertical Deflection Board also houses the convergence amplifiers that drive correction coils.

The System Power Supply provides all DC power below 200V to the projector. This includes the supply to the arc lamp/ignitor and the supply to the High Voltage Power Supply.

The High Voltage Power Supply provides all voltages of 200V and higher. This includes all CRT bias voltages except the cathode.

Image and sync inputs arrive in the projector at the Video Processor Board. Inclusion of the Decoder Board is optional. User communication is accomplished by on-screen displays, LED display output, IR remote input, or RS232 Input/Output. All of these devices are separate from, but communicate directly with the System Controller Board.

The detailed functional description of the subassemblies are covered below in the following order:

1.System Power.

2.Card Cage and Circuit Boards.

3.CRT Assembly.

4.Arc Lamp.

2.4System Power

System Power Supply

The System Power Supply provides the connection between the external power source and the projector. The System Power Supply provides all internal DC power to the projector with the exception of that provided by the High Voltage Power Supply (Section 2.4.3). This includes the low voltage power to the electronics, the supply power to the HVPS, and the Arc Lamp power.

The System Power Supply is a AC-DC power supply with an input rectifier and protection circuit and several separate switchers; one (1) for Arc Lamp power, one

(1)for +5V Standby power, one (1) for +24V Standby power, and others for the other low voltages.

All of the power supply outputs are protected against overvoltage and overcurrent. Overcurrent protection is a foldback circuit that limits the output current by reducing the output voltage when an overcurrent condition is detected. An overvoltage condition at the output of the supply will cause the affected voltage to be shut down until input power is removed and reapplied.

Model 330, 340SC and 370SC Service Manual 2–5