Genius ISO XFR-75W VIDEO INTERFACE CIRCUIT, FUNCTION, DESCRIPTION + & - Analog, Video, Amps, +12V

VIDEO INTERFACE CIRCUIT, FUNCTION, DESCRIPTION (+ & - Analog).

The video interface circuit is a general purpose RGB type input circuit. This circuit connects the external video signal to the video amplifiers. It can accept, DC or AC coupled positive going analog, negative going analog, and 4 line TTL.

The particular mode of operation is selected by inserting jumpers, different value components, and solder bridges. The Production Assembly Drawings (PADs) are given in the appendix which describe the component differences.

SIMPLIFIED VIDEO INTERFACE CIRCUIT:

Black Level (5.6V)

1. NEGATIVE GOING ANALOG MODE.

Saturated Color (1V)					+12V	RED channel shown		16	VIDEO
				7.5V BIAS LINE					AMPS
	3.5V
						Blue channel only		6
RED
		271			200Ω	3.6K	MG 12		MASTER
VIDEO
				6.3V						GAIN&
INPUT	301Ω				C5346
		340Ω	2						BLANKING
	278	236	3		241				4.7K
				-Analog Black Level	(-A BL)					+12V
									239
										G

In the negative analog mode, the video signal has a black level (5.6V) which is the -A BL voltage. The saturated color is the lowest input voltage (.9V-1.1V). The current amplitude to the video amplifiers is defined by resistors 278 & 236 and the master gain voltage.

For the blue channel only, 15% of the output current is subtracted by resistor 239 .

Signal sources with 8 bit drivers, that use 2 bits for the blue channel use this 15% offset.

To prevent input line ringing from exceeding the saturated color voltage limit, a clamp diode

271has been added.

	Saturated Color (.70V)
			2. POSITIVE GOING ANALOG MODE.
Black Level (0V)			+12V	RED channel shown		16	VIDEO
			7.5V BIAS LINE
							AMPS
	15.8K		11
	261		+ANALOG ENABLE
RED
	270Ω	15KHz	200Ω	3.6K	MG 12		MASTER
VIDEO	75Ω	31KHz .44V					GAIN &
INPUT	278		2				BLANKING
			C5346
	0-11V or 12V		241
		15.8K
		223	1
	75Ω			The black level voltage is set by resistor
		75.0Ω	J
	288	226	0Ω	divider 223 &	226 to compensate for the
				bias current voltage drop. An optional,
				variable black level, is accomplished with the
In the positive analog mode, a bias current of				black level adjustment pot.
.6mA flows to the input pin 2. This current is				The input termination resistor 288
set by resistor		261 at the +Analog Enable		reduces video line ringing and produces a
input pin 11. The .6mA produces a voltage,				dark screen when the video input connector
across the parallel resistance of the game and				is disconnected.
288 plus resistor 278 , at pin 2. If the				The normal saturated color is set at .70
external source resistance is 75 ohms, the black				volts. Higher saturated color levels can be
level voltage at pin 2 is .18V for 15KHz and				accommodated with resistor or gain changes.
.07V for the 31KHz.

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