Hughes JVC Projector 250 Sc Service Manual

Chapter 7---Troubleshooting
Model 250 Service Manual 7-13
to the Arc Lamp Power Supply low. The Arc Lamp Power Supply delivers 170 V
to the Igniter, which generates a 32 kV pulse to the Arc Lamp and the Arc Lamp
lights. Once the Arc Lamp lights, the Arc Lamp Power Supply, the /LAMP_LIT
signal goes low and the voltage to the Igniter drops to between 25 V and 31 V.
The voltage from the Arc Lamp Power Supply stays at a steady output of 2 kW
during normal operation of the projector.
When the projector...

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Image Path
Figure 7-11  
RGB Image path from VIC to CRT.
The image signals can be in the form of separate red, green and blue component
signals with separate horizontal and vertical sync signals or they can be a
composite image signal with all the image and sync signals combined into one
input signal. The image signals, if not already separate, are separated into red
green and blue color components, and horizontal and vertical syncs in the VIC....

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Deflection Path
Figure 7-12  
CRT 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...

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The Horizontal Vertical Deflection PCB outputs H_OUT_FLYBACK to the Scan
Reversal PCB. This is the horizontal deflection waveform that drives the
horizontal CRT deflection yokes. The H_RED+, GRN+, and BLU+ are the
horizontal deflection returns. The outputs of the vertical amplifier are V_RED+,
GRN+, and BLU+. The returns are V_RED-, GRN-, and BLU-.
The Convergence Deflection PCB receives a sample of the vertical frequency
from the Raster Timing...

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Figure 7-13  
CRT Deflection path between Horiz/Vert Deflection PCB,
Convergence Deflection PCB and Scan Reversal PCB. 

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Figure 7-14  
CRT Deflection path between the Scan Reversal PCB and CRT. 

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CRT Protection
Figure 7-15  
CRT Protection path
The CRT Protection circuit is designed to protect the CRTs in case any of the
CRTs is not receiving a horizontal or vertical deflection waveform. If there are no
deflection waveforms, the electron gun inside the CRT will shoot an electron
beam at the center of the CRT, burning a spot in the CRT phosphor that will be
visible on the screen. The CRT Protection circuit also protects the CRTs from...

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Amplifier PCB the /SWEEP_OK becomes the /VA_OK signal and checks the
supply voltages such as +15 V, +6.2 V and +80 V.  The /VA_OK LED
illuminates (see Video Amplifier PCB LED) if the supply voltages are present and
the /SWEEP_OK is low. The /VA_OK also goes to the High Voltage Power
Supply. On the High Voltage Power Supply, a logical “high” shuts down the high
voltage amplifier that generates the Anode, Focus, and G
2 voltages. The /VA_OK
signal...

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Figure 7-16  
CRT Protection path between the Scan Reversal PCB and CRT. 

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7.4 Error Codes
For certain errors that may occur in the Model 250 Projector the software
provides error codes that are helpful in determining the nature of the problem.
These error codes can be seen on the left side of the monitor screen when using a
PC connected to Port A or Port B.
Table 7-1
  Error Categories:
Category
NumberError Category Description
1 CEXEC Operating System.
2 FLASH HW Flash Memory HW driver.
3 IIC HANDLER IIC Handler for...