Hughes JVC Projector 250 Sc Service Manual

Chapter 7---Troubleshooting
Model 250 Service Manual 7-3
Figure 7-1  Rear Panel layout
Control Out -  The Control Out terminal is another RS232 port similar to the
Terminal In port except that it can not be used to Import/Export setup data.
Tethered Remote Jack - The Model 250 projector is shipped with an IR Remote
Control. This IR Remote can be used with an optional 150 ft. cable that will plug
in the Tethered Remote Jack.
IR Detector - This sensor detects commands from the IR Remote Control included...

Chapter 7---Troubleshooting
7-4 
Model 250 Service Manual
Figure 7-2  
Dip Switch Block  on System Controller PCB.
Reset Switch - The Reset Switch resets the CPU if the projector locks up and does
not respond to an IR Remote, PC or Laptop computer. If the rear panel is in place,
the CPU can also be reset by cycling the AC Circuit Breaker off and back on
again.
  CAUTION!  If the Arc Lamp was operating or recently
turned off (the cooling fans were still running) at the time the CPU
locked up, it is very...

Chapter 7---Troubleshooting
Model 250 Service Manual 7-5
Video Processor PCB LEDs
Figure 7-4  
Video Processor Test Points and LEDs.
Video Processor - Test Points
The test points on the Video Processor PCB are visible and accessible from the
left side of the Electronics Module when the rear projector cover is removed. The
test points can be grouped into four categories: 

Chapter 7---Troubleshooting
7-6 
Model 250 Service Manual
Sync - There are three sync test points: H sync for the horizontal sync pulse, V
sync for the vertical sync pulse, and G sync, which is a combination of the
horizontal and vertical sync pulses that are carried with the green image signal.
External - There are three external image test points: R ext, for the red external
image signal, G ext for the green external image signal, and B ext for the blue
external image signal. The external signal is the...

Chapter 7---Troubleshooting
Model 250 Service Manual 7-7
Raster Timing Generator PCB LEDs
Figure 7-6  
 Raster Timing Generator LEDs. 

Chapter 7---Troubleshooting
7-8 
Model 250 Service Manual
Raster Timing Generator PCB LEDs
Band LEDs
 The range horizontal scan frequencies accepted by the Model 250 projector is
divided into four “bands”. The four LEDs  (A, B, C, & D) toward the front of the
projector on the Raster Timing Generator PCB indicate which range of horizontal
scan frequencies the input source is operating. The four bands of horizontal
frequencies are
Band A = 15-25 kHz
Band B = 26-29 kHz
Band C = 29-56 kHz
Band D = 56-90 kHz...

Chapter 7---Troubleshooting
Model 250 Service Manual 7-9
Convergence Deflection PCB LED
Figure 7-7  
Convergence Deflection PCB LED.
The Convergence Deflection PCB has only one LED. It illuminates green when
power (±15 V) is present on the PCB. 

Chapter 7---Troubleshooting
7-10 
Model 250 Service Manual
Video Amplifier PCB LED
Figure 7-8
  Video Amplifier PCB LED.
The VA_OK LED on the Video Amplifier PCB is illuminated green when all the
CRT deflection circuits are operating properly (/DEFL_OK), the supply voltages
(±15 V, +6.2 V, and +80 V)  are present at the Video Amplifier PCB, and all the
CRT Yoke connectors are properly installed (see Figure 7-15 and Figure 7-16). 

Chapter 7---Troubleshooting
Model 250 Service Manual 7-11
Backplane PCB LEDs
Figure 7-9  
Backplane PCB LEDs on right side (exposed side)of PCB.
The Backplane has two status LEDs, the /LV_OK signal from the Low Voltage
Power Supply, and the /HV_OK signal from the High Voltage Power Supply. The
Backplane also has several connectors that can be used for probing signals and
voltages (see Figure 7-18 and associated signals and voltages). 

Chapter 7---Troubleshooting
7-12 
Model 250 Service Manual
7.3 Diagrams
Command ON Timing
Figure 7-10  
POWER ON and POWER OFF command timing diagram.
When the AC Circuit Breaker is powered ON, the Low Voltage Power Supply
generates a +5.1 V Standby voltage that goes to the System Controller PCB to
power the CPU and IR Detectors. The Low Voltage Power Supply also puts out
the +24 V Standby voltage (/FAN_ENA goes low) that provides power to the
cooling fans. The cooling fans run from the time the AC...