JVC 250 service manual Printed Circuit Boards PCB

Chapter 2---System Description

Printed Circuit Boards (PCB)

The Model 250 Projector has eight main PCBs:

!System Controller PCB - System Controller PCB controls much of the electronics system. It uses digital and analog circuitry to generate Menu and internal pattern overlays, and directs convergence correction and shading information. It controls the IIC data bus that sends geometric correction and VIC selection data. The System Controller PCB controls and monitors the status of power supply operations during and after the projector is powered ON.

!Raster Timing Generator PCB - The Raster Timing Generator PCB generates an internal sync for the PLL (Phase Lock Loop) circuitry. It provides sync detection and selection. It also generates the blanking pulse, provides horizontal and vertical phase adjustments, and Interlace detection.

!Video Processor PCB - The Video Processor PCB receives external image and sync signals and sends horizontal sync, vertical sync, and green sync signals to the Raster Timing Generator PCB. It adds Contrast, Brightness, Sensitivity and Threshold adjustments to the image signals and sends the image signals, G2 control lines, and G1 bias to the Video Amplifier PCB.

!Horizontal Vertical Deflection PCB - The Horizontal Vertical Deflection PCB supplies the deflection waveforms that drive the deflection yokes on the CRTs for the horizontal and vertical raster. It integrates the geometry correction such as pincushion, keystone, and vertical linearity onto the horizontal deflection waveform and adjusts the horizontal and vertical center raster.

!Convergence Deflection PCB - The Convergence Deflection PCB generates the horizontal and vertical convergence correction waveforms. It generates the horizontal and vertical Dynamic Focus Parabola used by the

High Voltage Power Supply. The Convergence Deflection PCB also provides the ILA® bias and sensitivity.

!Scan Reversal PCB - the Scan Reversal PCB reverses the deflection waveforms for both the horizontal and vertical axes for floor/ceiling mounting and front/rear mounting. It also provides scan failure detection to protect the CRT.

!Video Amplifier PCB - The Video Amplifier PCB amplifies the video signals and drives the cathodes for all three CRTs. It senses the cathode beam current and regulates the G1 and G2 for all the CRTs. The Video Amplifier PCB also provides phosphor protection for all three CRTs and CRT interface for the Focus, Heater Voltage, and Arc ground.

!Backplane - The Backplane sits in the back of the Electronics Module. The System Controller PCB, Raster Timing Generator PCB, Video Processor PCB and the VICs plug into directly the Backplane PCB. It

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