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 minutes.
3. Select the Focus pattern (test pattern #6).
4. Zoom the Projection Lens to the widest angle and adjust the Projection
Lens focus for the sharpest image.
5. View Green. Hide Red and Blue.
6. Adjust the Green Electronic Focus located on the side of the High Voltage
Power Supply (see Figure 3-5 and 3-6) for a sharp focus of the Focus
pattern at the center of the screen.
7. Repeat the above steps for Red and Blue.
Figure 5-30  
View of CRTs, Relay lenses and ILA® Assemblies. 
						

							Chapter 5---Electronics
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 Needed
#0 Pozi-drive Phillips-head screwdriver
Parts Needed
CRT  p/n 105199
To remove and replace a CRT:
1. Power OFF the projector by IR Remote or PC, and allow the cooling fans
to run until they shut off automatically.
2. Turn the AC Circuit Breaker to the OFF position and unplug the AC
Power Cord.
3. Remove front and rear covers.
4. Tilt the Electronic Module up and lock it in place.
5. Loosen the two Pozi-drive Phillips-head screws from the top of the High
Voltage Power Supply cover. Remove the one Pozi-drive Phillips-head
screw at the bottom of the cover.
6. Remove the CRT Anode cable of the CRT being replaced from the High
Voltage Power Supply.
7. Disconnect the Yoke plug and cable harness from the Scan Reversal PCB
for the appropriate CRT (see Figure 5-25).
8. Remove the wires from the cable clamp for the CRT/Yoke Assembly
being removed.
9. Loosen the CRT Holder Ring (knurled knob in Figure 5-29).
NOTE:
 The CRT Holder Ring should be only hand-tight. If it is not
possible to remove by hand, place a Flathead screwdriver in the slots on
the CRT Holder Ring and tap lightly to help loosen it. Do not use a tool of
any kind to tighten this ring - hand tighten only.
10. Carefully remove the CRT/Yoke Assembly by sliding it backward and
upward as far as possible before unplugging the CRT socket connector
from the neck. 
						

							Chapter 5---Electronics
5-58 Model 250 Service Manual
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 break any of these connections.
  CAUTION!  Use extreme caution to avoid bumping
the CRT/Yoke Assembly while removing it (
see Warning at the
beginning of this procedure).
11. After removing the CRT/Yoke Assembly, carefully disconnect the CRT
socket connector and the ground wire that connects the CRT to the socket
connector.
NOTE:
 It may be helpful to have another person assisting for step 9. One
person can disconnect the CRT socket connector and ground wire, while
the other person holds the CRT/Yoke Assembly firmly.
12. After verifying that all cables are out of the way, remove the CRT/Yoke
Assembly from the projector.
13. Reinstall the CRT/Yoke Assembly in the reverse order.
NOTE:
 When reinstalling the CRT/Yoke Assembly, plug the CRT ground
wire into the CRT Socket Connector first, then partially plug the Green
socket connector into the CRT. Inserting the CRT fully into the socket
connector will be easier when the CRT is completely installed.
14. Perform a CRT Mechanical focus adjustment and CRT Rotation after
replacing the CRT/Yoke Assembly. Because replacing the CRT/Yoke
Assembly can disturb other focus adjustments, check the CRT Mechanical
Focus on the other two colors to verify that they are still correct.
15. Check the on-screen horizontal size and adjust the Horizontal Size
Adjustment Coils on the Scan Reversal PCB if necessary.
5.11  Video Input Cards (VICs)
The VIC is the interface between the input source and the projector. Several input
source format are accepted such as separate RGBHV, Composite, YPbPr, and S-
Video.
The Model 250 accepts six different VICs;
!
 Wide Bandwidth RGBHV (Standard)
!
 Graphics Enhancer Plus RGBHV(Standard)
!
 4-Input (Quad) RGBHV (Optional) 
						

							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 VIC selection
Figure 5-31  
RGBHV VIC I/O Diagram.
Figure 5-32  
RGBHV VIC faceplate. 
						

							Chapter 5---Electronics
5-60 Model 250 Service Manual
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 to the Video Processor PCB (0.7-1.0 Vpp).
GRN_VIC - green image to the Video Processor PCB (0.7-1.0 Vpp).
BLU_VIC - blue image to the Video Processor PCB (0.7-1.0 Vpp).
H_VIC - horizontal sync to the Video Processor PCB
V_VIC - vertical sync to the Video Processor PCB
/SEL_VIC - VIC select line to the Video Processor PCB
RGBHV VIC - Operation
The RGBHV VIC receives the separate red, green, blue image inputs and
horizontal, and vertical sync inputs from the source input device and passes them
directly through to the Video Processor PCB without any signal processing. The
VIC receives a SELECT command from the System Controller PCB through the
IIC data bus to activate the VIC. The VIC sends a /SEL_VIC to an internal Input
Switcher (Mux) on the Video Processor PCB tell it which VIC is selected. An
operator selects the VIC in the Channels Menu (see section 4-6 in the User’s
Guide).
A green LED is illuminated when the VIC is selected.
RGBHV VIC - Service Adjustments
There are no service adjustments on the RGBHV VIC
RGBHV VIC - Remove and Replace
Tools Needed
#0 Posi-drive Phillips-head screwdriver 
						

							Chapter 5---Electronics
Model 250 Service Manual 5-61
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 the VIC out of the Electronics Module.
7.  Reverse the process to install the VIC.
Graphics Enhancer Plus RGBHV VIC
Grahics Enhancer Plus 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 VIC selection
!
 Graphics Enhancement for black-on-white graphics and text.
Figure 5-33  
Graphics Enhancer Plus I/O Diagram. 
						

							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 - IIC data line
IIC SINT - IIC interrupt line
Graphics Enhancer Plus VIC - Outputs
RED_VIC - red image to the Video Processor PCB (0.7-1.0 Vpp).
GRN_VIC - green image to the Video Processor PCB (0.7-1.0 Vpp).
BLU_VIC - blue image to the Video Processor PCB (0.7-1.0 Vpp).
H_VIC - horizontal sync to the Video Processor PCB
V_VIC - vertical sync to the Video Processor PCB
/SEL_VIC - VIC select line to the Video Processor PCB 
						

							Chapter 5---Electronics
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 the Black Enhance and White Enhance
commands in the Picture Menu. The graphics enhancements are for black text and
graphics on a white background.
The processed red, green, and blue image signals are sent to the Video Processor
PCB. The horizontal and vertical sync pulses go straight through the VIC to the
Video Processor PCB without modification.
The VIC receives a SELECT command from the System Controller PCB through
the IIC data bus to activate the VIC. The VIC sends a /SEL_VIC signal to an
internal Input Switcher (Mux) on the Video Processor PCB. This tell the Video
Processor PCB which VIC is selected. An operator selects the VIC in the
Channels Menu (see section 4-6 in the User’s Guide).
A green LED is illuminated when the VIC is selected.
Graphics Enhancer Plus VIC - Service Adjustments
There are no physical service adjustments on the Graphics Enhancer Plus VIC
Graphics Enhancer Plus VIC - Remove and Replace
Tools Needed
#0 Posi-drive Phillips-head screwdriver
Parts Needed
Graphics Enhancer Plus VIC  p/n 106183
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 automatically.
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 the VIC out of the Electronics Module.
7. Reverse the process to install the VIC. 
						

							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 - 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 
						

							Chapter 5---Electronics
Model 250 Service Manual 5-65
IIC CLK - IIC clock line
IIC DATA - IIC data line
IIC SINT - IIC interrupt line
Figure 5-36  
4-Input (Quad) RGBHV VIC.