JVC 250 - Horizontal and Vertical Deflection Control

Chapter 5---Electronics
Model 250 Service Manual 5-21
5.6 Horizontal Vertical Deflection PCB
Horizontal Vertical Deflection PCB - Main Functions
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Drive the main horizontal deflection coils to provide horizontal raster scan
for the CRTs
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Drive main vertical coils to provide vertical raster scan for the CRTs
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Horizontal raster centering for all three colors
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Switch mode power supply generating the required proportional DC
supply
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Horizontal width adjustment
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Horizontal retrace switch network
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Left/right pincushion and keystone correction
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Vertical linearity adjustments individually for all three colors.
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Vertical raster centering for all three colors
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IIC interface.
Horizontal Vertical Deflection PCB - Inputs
H_BAND:0-3 - horizontal scan frequency bands, from Raster Timing Generator
PCB.
/H_ENABLE - from the Raster Timing Generator PCB, enables the horizontal
deflection supply. Low = enabled deflection, High = disabled deflection.
H_DRIVE - square wave from the Raster Timing Generator PCB, 50% duty cycle
synchronized to the selected horizontal sync.
H_F2V - a DC voltage from the Raster Timing Generator PCB, proportional to
horizontal frequency
H_LOCK (neg.) - Deflection Yoke Connector Interlock return from the Scan
Reversal PCB.
DEFL_OK - deflection status signal from the Scan Reversal PCB (high = good,
(about 2 V), low = no scan).
V_RAMP - vertical ramp waveform from the Convergence Deflection PCB,
(about 4 Vpp).
V_PARAB - vertical parabola waveform from the Convergence Deflection PCB,
(about 4 Vpp).
FRONT/REAR - front or rear projection status line from the Scan Reversal PCB.
(FRONT = low, REAR = high).
FLOOR/CEILING - floor or ceiling projection status line from the Scan Reversal
PCB. (FLOOR = low, CEILING = high).