JVC Model 200 service manual System Controller PCB

Chapter 2---System Description

2.3.6 System Controller PCB

The System Controller Board (SCB) is located in the electronic card cage (Figure 5-1).

The Electronics System is controlled by the SCB. The SCB uses digital and analog circuits to direct the operation of image and raster generation circuits and to control the input/output of power supply operation.

The SCB sets the operating parameters of the image, such as brightness and contrast. It also produces internal test patterns and generates on-screen display overlays. The SCB sets the timing for the raster generation to adjust phase, geometric corrections, shading corrections, and convergence. The program memory and the memory for all convergence and shading maps are located on the SCB.

The following functions are performed or controlled by the System Controller:

•Enables control for the Low Voltage Power Supply, Arc Lamp and cooling fans.

•Fault monitors the HVPS, LVPS, Arc Lamp, and fans.

•Provides interboard communication via the IIC serial bus.

•Controls Zoom and Focus of the Projection Lens.

•IIC Interface control

•Provides Video Overlays

•X and Y convergence control

•Threshold and Sensitivity for shading

•I/O control

•Two RS-232 serial interface ports

•Infrared (IR) remote control interface. Accepts input from front or rear IR detectors.

•A 5-wire JTAG interface port for CPU emulation support.

•External 3 color system status LEDs. Green indicates normal, yellow is standby and red indicates a fault condition.

•External Service Mode switch (see Figure 5-1). Pressing this switch during a power-up sequence brings the system up in a diagnostic mode (for maintenance) rather than a normal operating mode.

The SCB I/O diagram (Figure 2-12) and the list of Inputs and Outputs (Table 2-9) provide information for the technician to perform module-level troubleshooting.

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