JVC 250 service manual Quad Standard Decoder VIC - Inputs, Quad Standard Decoder VIC - Outputs

Chapter 5---Electronics

Quad Standard Decoder VIC - Inputs

Comp - input for Composite image signal includes sync pulses (.07-1 Vpp) Yin - input for Luminance or brightness information of S-image (0.7-1 Vpp) Cin - input for Chrominance or color information of S-image (0.3-0.6 Vpp)

+15 V - power for analog circuitry

+5.1 V - power for digital circuitry

IIC CLK - IIC clock line

IIC DATA - IIC data line

IIC SINT - IIC interrupt line

Quad Standard Decoder VIC - Outputs

RED_VIC - red image to Video Processor PCB (0.7-1.0 Vpp).

GRN_VIC - green image to signal Video Processor PCB (0.7-1.0 Vpp).

BLU_VIC - blue image to Video Processor PCB (0.7-1.0 Vpp).

SYNC - composite horizontal and vertical sync to Video Processor PCB.

/SEL_VIC - VIC select line to Video Processor PCB.

Quad Standard Decoder VIC - Operation

The Quad Standard Decoder VIC accepts two source input formats, Composite and S-image. The Composite format combines the image (red, green, and blue) signals and the sync pulses (horizontal and vertical) into one signal. The S-image signal has two separate inputs, one contains the color information (Cin), and the other input contains the black and white information (Yin). The sync pulses are combined with the Yin. Both the Composite and S-image formats may be in a variety of different signal standards such as NTSC (U.S.), PAL (European), SECAM, or 4.43 NTSC. The VIC accepts all of these standards. The Quad Standard Decoder VIC converts Composite and S-image to the RGBHV format. The selection of the VIC and inputs is controlled by the System Controller Board via the IIC serial bus interface. An operator selects the VIC and input in the Channels Menu (see section 4-6 in the User’s Guide).

The Quad Standard Decoder VIC strips the sync pulses that are combined with the black and white information (Yin) and sends them to the Video Processor PCB as a composite sync signal. The Video Processor PCB separates the composite sync signal and sends it to the Raster Timing Generator PCB.

The Quad Standard Decoder VIC also does signal processing with the Tint, Color, and Sharpness options in the Picture Menu. The Tint control adjusts the tint of the colors displayed. Facial tones will vary from slightly green at zero to slightly red at 255. The Color control adjusts the amount of color saturation or color intensity. Colors will be almost grayscale at zero and very saturated at 255. The Sharpness control adjusts the high frequency peaking of the black and white details.

The Quad Standard Decoder VIC has two LEDs. The Composite LED illuminates green when the Composite input is selected. The S-image LED illuminates green

Model 250 Service Manual 5-71