JVC 250 service manual Deflection Path

Chapter 7---Troubleshooting

Deflection Path

Figure 7-12CRT Deflection path from Raster Timing Generator PCB.

The Raster Timing Generator PCB receives the horizontal and vertical sync pulses from the Video Processor PCB, and uses a Phase Locked Loop circuit to lock to the horizontal sync. It sends a sample of the horizontal frequency (H_DRIVE) to the Horizontal Vertical Deflection PCB to set the timing of the Horizontal Amplifier, a Switched Mode Power Supply that generates the horizontal deflection sawtooth waveform. The Raster Timing Generator PCB divides the range of horizontal scan frequencies into four groups or bands because the retrace or flyback timing varies dramatically from the lowest frequency (15 kHz) to the highest frequency (90 kHz).

The Horizontal Vertical Deflection PCB generates the horizontal waveforms that drive the CRT Yokes. Many of the geometric corrections are integrated into the horizontal waveform at the Horizontal Vertical Deflection PCB such as Pincushion, Keystone, Skew, and Bow. The vertical size is be adjusted on the Horizontal Vertical Deflection PCB.

Model 250 Service Manual 7-15