NEC FP1355 Service Manual

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Contents

NEC FP1355 Service Manual Manual pdf 36 page image

1 - 30(4) North-south horizontal field landing cancelThe north-south horizontal field landing cancel carries out automatic adjustment of color shading andcolor shift occurring appeared in the opposite derection at the top and bottom end of the monitordisplay surface in the horizontal direction.The detecting voltage and direction of the north-south horizontal field (IC214 pin 2) are detected byIC214 (geomagnetic sensor unit), the detecting voltage is read by IC101 pin 18 (CPU_ADC), and thedirect current of ±20mA (max) flows in each corner purity coil according to the specified controlprogram. (Four-corner interlock control)• The left upper corner on the display surface is controlled with 0 to 5V of 2.5V referenceby IC101 pin 6 (PWM-DAC), and the DC current of the above value is made to flow tothe purity coil on the left upper corner by IC803 pin 2.• The right upper corner on the display surface is controlled with 0 to 5V of 2.5V reference by IC101 pin 7 (PWM-DAC), and the DC current of the above value is made toflow to the purity coil on the right upper corner by IC803 pin 8.• The left lower corner on the display surface is controlled with 0 to 5V of 2.5V referenceby IC101 pin 8 (PWM-DAC), and the DC current of the above value is made to flow tothe purity coil on the left lower corner by IC801 pin 2.• The right lower corner on the display surface is controlled with 0 to 5V of 2.5V referenceby IC101 pin 9 (PWM-DAC), and the DC current of the above value is made to flow tothe purity coil on the right lower corner by IC801 pin 8.1.5.3 Earth magnetism cancel circuitThe earth magnetism cancel circuit has a south-north horizontal magnetic field cancelingfunction and a vertical magnetic field canceling function.IC214 (earth magnetism sensor unit) detects the voltage and direction of the south-north hori-zontal magnetic field (IC214 pin 2) and the vertical magnetic field (IC214 pin1), and IC101 pins18 and 19 (CPU_ADC) reads the detected voltage to automatically control the following cancel-ing function according to the specified control program.Here, the output voltage of IC214 (earth magnetism sensor unit) operates as follows.• South-north horizontal magnetic field (IC214 pin 2): 0.8V(-0.04mT) to 2.5V(+/-0.00mT) to4.2V(+0.04mT)• Vertical magnetic field (IC214 pin 1) : 3.3V (-0.04mT) to 2.5V (+/-0.00mT) to 0.5V (+0.10mT)

(a) Horizontal magnetic field landing cancelThe horizontal magnetic field landing cancel circuit is a circuit to compensate for the colorshade and deviation that appear in the horizontal direction that becomes the oppositedirection at the upper and lower ends on the monitor display surface, and the automaticadjustment is done by DC current flowing to the corner purity coil that is wound around thedisplay surface. (synchronized control for four corners)(Refer to 1.5.2 (4) for detail.)(b) Horizontal magnetic filed convergence cancelThe horizontal magnetic field convergence cancel circuit is the circuit to compensate forthe misconvergence that results after the vertical convergence of RED and BLUE in thewhole display area of the monitor deteriorates, and it is automatically adjusted by DCcurrent flowing to the 4V convergence compensation coil mounted on DY. It is controlledwith the DC component (V-CONVERGENCE) by IC601 pin 60 (4V_SC), and DC current of+/-30mA (max) is flowen to the 4V convergence compensation coil by IC8A1 pin 6 (PowerOpamp).