Hughes JVC Projector 250 Sc Service Manual

Chapter 5---Electronics
5-56 Model 250 Service Manual
CRT Electronic Focus
The Electronic Focus is factory-set and normally will not need to be adjusted
except after component replacement, maintenance, or if wide temperature
variations exist between the factory and the field location. View one color at a
time.
Tools Needed
Medium Phillips-head screwdriver
To perform the Electronic Focus adjustment:
1. Remove the front and rear cover.
2. Power the projector ON and allow it to stabilize for at least 15...

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Model 250 Service Manual 5-57
CRT/Yoke Assemblies - Remove and Replace
Three CRT/Yoke Assemblies are located in the CRT Assembly area below the
card cage (see Figure 5-30).
  WARNING!!!  Handle the CRT/Yoke Assemblies with
extreme caution. If they are dropped, they can implode and flying glass
can cause severe injury to personnel. Be careful not to bump or drop the
CRT. Immediately after removal, place the CRT/Yoke in a safe area.
Procedure to remove a CRT/Yoke Assembly:
Tools...

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NOTE:
  For the Green CRT/Yoke Assembly only, it is best to perform
Step 10 with the CRT socket connector still connected to the Green CRT
and the ground wire still connected from the CRT to the socket connector.
Because the Green CRT socket connector is close to the rear of the
projector, it is easier to disconnect the socket connector from the CRT
after the CRT/Yoke Assembly is loose and moved away from the rear of
the projector. Be careful not to...

Chapter 5---Electronics
Model 250 Service Manual 5-59
!
 YPbPr (Optional)
!
 Quad Standard Decoder (Optional)
!
 Quad Standard Decoder/Line Doubler (Optional)
The are three VICs slots on the Model 250, however the 4-Input RGBHV, and the
Quad Standard Decoder/Line Doubler require two slots.
Standard RGBHV VIC
RGBHV VIC - Main Functions
!
 Interface for Red, Green, and Blue image inputs
!
 Interface for Horizontal and Vertical synchronization pulses
!
 IIC Serial Data Bus communication
!
 LED indication of...

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RGBHV VIC - Inputs
R - red image from source input (0.7-1.0 Vpp).
G - green image from source input (0.7-1.0 Vpp).
B - blue image from source input (0.7-1.0 Vpp).
H - horizontal sync from source input
V - vertical sync from source input
+15 V - (not used)
-15 V - (not used)
+5.1 V - power for digital circuitry
+5.1 V Stdby (not used)
IIC CLK - IIC clock line
IIC DATA - IIC data line
IIC SINT - IIC interrupt line
RGBHV VIC - Outputs
RED_VIC - red image...

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Parts Needed
RGBHV VIC  p/n 102597
To remove the RGBHV VIC:
1. Power off the projector by IR Remote or PC, and allow the cooling fans to
run until they shut off.
2. Turn the AC Circuit Breaker to the OFF position and unplug the AC
Power Cord.
3. It is not necessary to remove the rear cover.
4. Disconnect the red, green blue, horizontal and vertical input BNC cables
from the VIC.
5. Remove the two retaining screws from the faceplate of the VIC.
6. Pull...

Chapter 5---Electronics
5-62 Model 250 Service Manual
Figure 5-34  
Graphics Enhancer Plus faceplate.
Graphics Enhancer Plus VIC - Inputs
R - red image from source input (0.7-1.0 Vpp).
G - green image from source input (0.7-1.0 Vpp).
B - blue image from source input (0.7-1.0 Vpp).
H - horizontal sync from source input
V - vertical sync from source input
+15 V - power for analog circuitry
-15 V - power for analog circuitry
+5.1 V - power for digital circuitry
+5.1 V Stdby
IIC CLK - IIC clock line
IIC DATA...

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Model 250 Service Manual 5-63
Graphics Enhancer Plus VIC - Operation
The RGBHV VIC receives the separate red, green, blue image inputs and
horizontal, and vertical sync inputs from the source input device. The image
signals go to a image enhancement signal processor that peaks the black details,
enhances white details, and minimizes white overshoot according to commands
received from the IIC data bus from the System Controller PCB. The commands
are generated by an operator through...

Chapter 5---Electronics
5-64 Model 250 Service Manual
4-Input (Quad) RGBHV VIC
4-Input (Quad) RGBHV VIC - Main Functions
!
 Interface for four sets of Red, Green, and Blue image inputs
!
 Interface for four sets of Horizontal and Vertical synchronization pulses
!
 VIC selection by IIC Serial Data Bus
!
 LED indication of VIC selection
Figure 5-35  
4-Input (Quad) RGBHV VIC faceplate (two VIC slots ).
 4-Input (Quad) RGBHV VIC - Inputs
Four sets of inputs
R - red image from source input (0.7-1.0 Vpp).
G -...

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IIC CLK - IIC clock line
IIC DATA - IIC data line
IIC SINT - IIC interrupt line
Figure 5-36  
4-Input (Quad) RGBHV VIC.