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To comply with DHEW regulations it is necessary to in- sure that the H.V. may not rise to the point where soft x-rays are generated by CRT. This would occur at 22.5 KV when sufficient beam current is present. This is taken care by a limiter resistor R900 which supplies current to oscillator circuit. As H.V. increases, current in oscillator circuit will increase causing more voltage drop across R900. This will limit max. voltage supply to oscillator which in turn hold down H.V. from going up. R900 value has been selected such that H.V. will not exceed max. 21 KV under any regulator fault condition. |
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Both X and Y channels are practically identical with only minor differences in input signal levels of ± 10V and ± 7.5V respectively to accomodate the 4/3 aspect ratio of the CRT. Because of this, we will investigate only the X channel. The amplifier is a direct coupled voltage to current con- verter. It is current through the yoke that will produce the magnetic field to deflect the electronic beam. The small signal response of the amplifier is DC to approximately 2 MHz with the large signal being limited mainly by yoke in- ductance and available supply voltage to a maximum slew rate of approximately 120 usec. for full deflection. |
The input signal of ± 10V is applied to P100-3 by a generator that is capable of delivering this voltage into a 1.3K Ohm load. R702, R700, R703, R704 and VDR700 has been used to make correction and to compensate inherent non- linearity characteristics of CRT for deflection. VDR700 is used to produce a closer 1st order approximate to the desire pre-distortion necessary to correct for the CRT deflection non-linearity and controlled by R700. |