Hughes JVC Projector 250 Sc Service Manual

Chapter 5---Electronics
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6. Pull the black card extractor handles back to disconnect the Video
Processor PCB connector and pull the PCB out of the Electronics Module.
7. Reverse the procedure to install the Video Processor PCB.
5.5  Raster Timing Generator PCB
Raster Timing Generator PCB - Main Functions
!
 Generates an internal sync pulse
!
 Detects and selects sync pulses
!
 Generates a phase locked sync
!
 Generates blanking pulse
!
 Provides horizontal and vertical phase...

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Figure 5-11  
Raster Timing Generator for other PCBs.
Raster Timing Generator PCB - Inputs
V_SYNC - input vertical sync from the Video Processor PCB.
H_SYNC - input horizontal sync from the Video Processor PCB.
G_SYNC - Sync-on-Green sync stripped from green video signal at the Video
Processor PCB.
ISYNC - 5 MHz clock from the System Controller PCB used to generate the
internal sync. 

Chapter 5---Electronics
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IIC_CLK - IIC clock line. Unidirectional clock line for control of synchronous
data transfer over the IIC bus.
IIC_DATA - IIC data line. Bi-directional serial line for synchronous data transfer
between System Controller PCB and Raster Timing Generator PCB.
+15 V (two inputs) - input power from LVPS for analog circuitry including the
Phase Lock Loop (PLL) circuit.
-15 V (two inputs) - input power from LVPS for analog circuitry including the
Phase Lock...

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Model 250 Service Manual 5-19
V_DRIVE - square wave negative going pulse to the Convergence Deflection
PCB, synchronized to the selected vertical sync with the pulse width of about four
horizontal periods.
Raster Timing Generator PCB - Operation
The Raster Timing Generator PCB generates a square wave that is phase-locked
to the horizontal sync pulse. It generates timing signals such as Blanking that goes
to the Video Processor PCB and Video Amplifier PCB, and the H_DRIVE signal...

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Vertical Deflection PCB to break the range of horizontal scan frequencies into
four smaller ranges called bands (see Figure 5-12).
Figure 5-12  
LEDs on the Raster Timing Generator PCB.
Raster Timing Generator PCB - Remove and Replace
Tools Needed
#1 Pozi-drive Phillips-head screwdriver
Parts Needed
Raster Timing Generator PCB - p/n 105238
To remove the Raster Timing Generator PCB:
1. Power OFF the projector by IR Remote or PC, and allow the cooling...

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5.6  Horizontal Vertical Deflection PCB
Horizontal Vertical Deflection PCB - Main Functions
!
 Drive the main horizontal deflection coils to provide horizontal raster scan
for the CRTs
!
 Drive main vertical coils to provide vertical raster scan for the CRTs
!
 Horizontal raster centering for all three colors
!
 Switch mode power supply generating the required proportional DC
supply
!
 Horizontal width adjustment
!
 Horizontal retrace switch network...

Chapter 5---Electronics
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IIC_CLK - IIC clock line
IIC_DATA - IIC data line
IIC_SINT - IIC interrupt
±15 V - input power from the Low Voltage Power Supply, for the analog
circuitry.
+5.1 V - input power from the Low Voltage Power Supply, for the digital
circuitry.
Figure 5-13  
Horizontal/Vertical I/O Diagram. 

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Figure 5-14  
Horizontal/Vertical I/O Diagram for Scan Reversal and Video
Amplifier PCBs. 

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Figure 5-15  
Physical layout of the Horizontal/Vertical PCB (note the Vertical Size
Adjustment Pots (Red-137, Grn-148, and Blu-160) on  the lower right).
Horizontal Vertical Deflection PCB - Outputs
/SWEEP_OK - signal to the Video Amplifier PCB, derived from the H_ENA
signal from the Raster Timing Generator PCB, and the DEFL_OK from the Scan
Reversal PCB.
WIDTH_CTRL - a DC voltage to the Convergence Deflection PCB that adjusts
the parabola waveforms...

Chapter 5---Electronics
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Horizontal Vertical Deflection PCB - Operation
The Horizontal Vertical Deflection PCB consists of a RGB horizontal deflection
amplifier and separate vertical deflection amplifiers.
The Horizontal Deflection Amplifier
The horizontal deflection amplifier is a switching mode power supply that varies
according to the input horizontal sync frequency. The horizontal supply generates
the sawtooth current-driven waveform that drives the horizontal deflection...