Genius 1993, ISO XFR-75W, 2093, 1493, 2793, 3693, 1793, ISO XFR-100W manual

Refer to the block diagram on page 15 (foldout) when reading this description.

A

The Video Interface is designed around a custom IC and will accept DC or AC coupled positive analog video signals. It can also be used with negative analog and 4 line TTL. This IC has a built in multiplier circuit for the master gain control and blanking functions. Resistors are used to protect the IC and to set the gain. The programmed gain is dependent on the input signal amplitude except with the TTL mode. Solder jumpers and component substations are used to program the Video Interface for the type of input signal to be received. The output of the IC drives the video amplifiers. This drive is a current where 0 mA is black and 10 mA is a saturated color.

B

The Video Amplifiers are of the push pull type. They are built partly on thick films and partly on the video PCB. Spreading out the amplifier reduces the component heat and improves the life of the unit. The bandwidth is 25 MHz with 40Vp-p output. The rise and fall times are 20nS.

C

The Beam Current Feedback circuit directs most of the beam current of each amplifier to the beam current buffer. The only time this current is measured, by the auto bias circuit, is during the time of the three faint lines at the top of the screen and three lines thereafter. The CRT auto bias circuit is designed to adjust the video amplifier bias voltage such that the beam current of each of the three guns is set to a specific programmed value.

D

The Beam Current Buffer converts the, high impedance low current, beam current signal into a low impedance voltage. This voltage is applied to the auto bias IC through a 200 ohm resistor. After the three lines of beam current are measured, the program pulse from the auto bias IC, produces a voltage drop across this 200 ohm resistor that equals the amplitude of the beam current voltage.

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