Hughes Jvc 200 Projector Service Manual

							Chapter 2---System Description 
GRN_THRES Similar to RED_THRES 
BLU_THRES Similar to RED_THRES 
 I/O DESCRIPTION 
IIC_DATA IIC data line. Bidirectional serial line for synchronous data  
  transfer between SCB and other circuit boards. See detailed  
 description for list of signals transferred and data direction 
IIC_CLK IIC clock line. Unidirectional clock line for  control of  
 synchronous data transfer over IIC bus. 
IIC_INT Interrupt output to SCB 
 Raster Timing Generator
INPUT  DESCRIPTION 
CLAMP Pulse signal input from the RTG board. Indicates the commanded 
 timing and duration of the DC RESTORE. 
BLANKING Pulse signal input from the RTG board. Indicates the commanded 
 BLANKING interval during the scan. 
OUTPUT DESCRIPTION 
H_SYNC Horizontal sync signal to RTG board 
V_SYNC Vertical sync signal to RTG board 
GRN_SYNC Green sync signal to RTG board 
GRN_INPUT Green video signal to RTG board 
 Video Amplifier
INPUT DESCRIPTION  
RED_BEAM Voltage signal proportional to cathode current averaged 
 over several horizontal lines in the red CRT. Voltage 
 level is + mV/µA 
GRN_BEAM Similar to RED_BEAM 
BLU_BEAM Similar to RED_BEAM 
/VA_OK Issued from the VAB to indicate VAB working properly 
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							  Chapter 2---System Description 
OUTPUT DESCRIPTION 
RED_VIDEO Red video output. 0 Volt to 1 Volt. 
GRN_VIDEO Similar to RED_VIDEO 
BLU_VIDEO Similar to RED_VIDEO 
RESTORE DC RESTORE control signal. When this signal is asserted, the 
 DC level of the video signal is clamped at the proper value 
 on the VAB. 
RED_G2 Red CRT G2 voltage adjust control signal. 
GRN_G2 Similar to RED_G2 
 BLU_G2  Similar to RED_G2 
 G1_BIAS   Control the adjustment of G1 voltage for all three CRTs 
   External Video
 INPUT  DESCRIPTION 
 RED_VIC #1  Red video input from video input card #1 
 GRN_VIC #1  Similar to RED_VIC #1 
 BLU_VIC #1  Similar to RED_VIC #1 
 RED_VIC #2  Similar to RED_VIC #1 
 GRN_VIC #2  Similar to RED_VIC #1 
 BLU_VIC #2  Similar to RED_VIC #1 
 RED_VIC #3  Similar to RED_VIC #1 
 GRN_VIC #3  Similar to RED_VIC #1 
 BLU_VIC #3  Similar to RED_VIC #1 
 H_VIC #1  Horizontal sync signal input from video input card #1 
 H_VIC #2  Similar to H_VIC #1 
 H_VIC #3  Similar to H_VIC #1 
 V_VIC #1 Vertical sync signal input from video input card #1 
 V_VIC #2  Similar to V_VIC #1 
 V_VIC #3  Similar to V_VIC #1 
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							Chapter 2---System Description 
 
 /SEL_VIC #1  Input signal from RGB VIC board which is used to select 
  input video source from VIC #1. 
 /SEL_VIC #2  Similar to /SEL_VIC #1 
 /SEL_VIC #3  Similar to /SEL_VIC #1  
 Low Voltage Power Supply 
INPUTS  DESCRIPTION 
+ 5.1 volts  Power supply to digital components 
+ 15 Volts  Power supply to analog components 
- 15 Volts  Power supply to analog components 
 
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							  Chapter 2---System Description 
2.3.5   Video Amplifier 
The Video Amplifier Board (VAB) is located at the back side of the 
projector under the necks of the three CRTs. It contains three 
separate video amplifiers, one each for red, green, and blue. The 
outputs from these video amplifiers connect directly to the CRTs 
and provide all electrical connections to the CRTS except for the 
anode voltages.  
The following functions are provided by VAB: 
• Amplification of video signals and driving the cathode of all 
three CRTs 
• Sensing the cathode beam current for all three CRTs 
• G1 regulator for all three CRTs 
• Blanking drive section 
• Phosphor protection for all three CRTs 
• G2 regulator and adjustment of black level (screen) for all 
CRTs 
• DC restoration for the video signals  
• CRT interface for focus, heater voltage and ARC ground 
The Video Amplifier Board I/O diagram (Figure 2-11) and the list 
of Inputs and Outputs (Table 2-8) provide information for the 
technician to perform module level troubleshooting. 
G1 Regulator for three CRTs 
The input supply for the G1 grid of the CRTs is G1_SUPPLY and 
is about -200V. The VAB regulates this supply to about -80V to -
30V. This supply can be adjusted by the G1_BIAS line. This 
adjustment provides the brightness control function. The G1_BIAS 
signal is an input of the VAB and is generated by the Video 
Processor Board. In the event of a failure, such as lack of 
deflection (a high on the /SWEEP_OK line), this output goes to the 
most negative value of the input supply (about -200V). 
G2 Regulator and  black level adjustment for CRTs 
The VAB also regulates the G2 grid of the CRTs. The supply for 
the G2 grids (about 1200V) is generated by the HVPS. This 
G2_SUPPLY is an input to the VAB. There are also three control 
inputs (RED_G2, GRN_G2, and BLU_G2). The G2 voltage of 
each CRT is adjusted individually by using these control lines. 
This adjustment provides black level control. The G2 output 
voltages are pulled down during shutdown mode. 
 
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							Chapter 2---System Description 
RED_VIDEOGRN_VIDEOBLU_VIDEO
BLANKINGG1 SUPPLYG1 BIAS
RESTORE
ARC_GND
BLU_CATHODE8BLU_GRID19BLU_GRID210
BLU_BEAM16
BLU_HEAT-7BLU_HEAT+6
ARC_GND3
GRN _CATHODE8GRN _GRID19GRN _GRID210
GRN_BEAM14
GRN _HEAT-7GRN _HEAT+6
ARC_GND3
RED _CATHODE 8RED _GRID1  9RED _GRID2 10
RED_BEAM        12
RED _HEAT-      7RED _HEAT+  6
ARC _GND   3
246
23
2112
13      GRN_G215      BLU_G2
1     G2 SUPPLY
11      RED_G2
19   /SWEEP_OK
3     + 8OV7     + 15V5     + 6.2V9     -15V
/VA_OK                18
J83
J68
J68
J85
J87
J68
J68
J84-1,J86-1,J88-1
J67
J68
J69
J68
FromVPB
From VPB
From HVPSFrom RTG
From VPB
FromVPB
From HVPS
From HVDB
FromLVPS
To VPB
To REDCRT
To VPB
To GRNCRT
To VPB
To BLUCRT
To VPB
To HVPS
VIDEO
AMPLIFIER
BOARD
 
Figure 2-11.   Video Amplifier PCB, Block Diagram. 
CRT interface for Focus, heater voltages and ARC ground 
The three CRT sockets are part of the VAB. They provide the 
necessary interface for the input of the three CRTs. The Focus 
voltage for each color is connected directly to the socket of each 
CRT. 
The VAB provides ARC grounds for each CRT which are used to 
protect against arcing of the CRT anode supply. 
IIC Interface 
The VAB does not use the IIC interface. All adjustments are 
accomplished by the control lines coming from the Video 
Processor Board. 
The Video Amplifier Board I/O  
This section provides a description of the inputs to and outputs 
from the VAB. The I/O descriptions are arranged by the 
source/destination of the signal. The assembly communicated with 
is used as the primary heading of each group of signals. Those 
signals are subdivided into inputs and outputs. Input refers to an 
Input to the VAB, output refers to an output from the VAB. 
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							  Chapter 2---System Description 
Table 2-8.  Video Amplifier I/O signals 
Video Processor Board 
INPUTS DESCRIPTION 
RED_VIDEO 
GRN_VIDEO 
BLU_VIDEO 
Video preamp signals. About 0.5 VPP 
G1_BIAS Brightness control line. 0 to 5 V DC 
RED_G2 
GRN_G2 
BLU_G2 
Black level (G2) control lines 0 to 3.1 V 
RESTORE Video DC restoration pulse. logic HC positive going  4% duty cycle 
OUTPUTS DESCRIPTION 
/VA_OK VAB status line. Low = good VAB. High = Bad VAB (This signal is 
called /HV_ENABLE at the HVPS). 
RED_BEAM 
GRN_BEAM 
BLU_BEAM 
Cathode beam current lines. about 1 volt per 100 UA 
High Voltage Power Supply  
INPUTS DESCRIPTION 
G1_SUPPLY Supply for G1 grid of CRTs. About -200 V 
G2_SUPPLY Supply for G2 (screen) grid of CRTs. About 1200 V 
RED_FOCUS 
GRN_FOCUS 
BLU_FOCUS 
Focus supply for CRTs. about 7 KV 
OUTPUTS DESCRIPTION 
ARC_GND CRT ground (anode supply return line) 
Horizontal/Vertical Deflection Board 
INPUTS DESCRIPTION 
/SWEEP_OK Deflection detection line. open collector, low = good deflection 
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							Chapter 2---System Description 
Raster Timing Generator Board  
INPUTS DESCRIPTION 
BLANKING Blanking signal. logic F type 
CRTs 
OUTPUTS DESCRIPTION 
RED_FOCUS 
GRN_FOCUS 
BLU_FOCUS 
Focus supply of CRTs. about 7 KV. 
RED_GRID1G
RN_GRID1BL
U_GRID1 
Grid 1 (G1) signal of CRTs. 
RED_HEAT+
GRN_HEAT+
BLU_HEAT+ 
Positive side of the heater voltage for CRTs. About 6.2 V. 
RED_HEAT-
GRN_HEAT-
BLU_HEAT- 
Negative side (return line) of the heater voltage for CRTs. Ground 
level. 
RED_ 
CATHODE 
GRN_ 
CATHODE 
BLU_ 
CATHODE 
Video output signals of the VAB. about 40 VPP with peak voltage of 
about 70 V. 
RED_GRID2 
GRN_GRID2 
BLU_GRID2 
G2 (screen) supply of CRTs. about 600 to 800 V 
OUTPUTS DESCRIPTION 
ARC_GRD Ground of CRTs ( anode supply return line). 
System Power Supply 
INPUTS DESCRIPTION 
+6.2 V +6.2 V supply line (heater voltage). 
+15 V +15 V supply for use by Video Amplifier Board. 
-15 V -15 V supply for use by Video Amplifier Board. 
+80 V +80 V supply for use by Video Amplifier Board. 
Interlocks and protection: 
None 
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							  Chapter 2---System Description 
2.3.6   System Controller PCB 
The System Controller Board (SCB) is located in the electronic 
card cage (Figure 5-1). 
The Electronics System is controlled by the SCB. The SCB uses 
digital and analog circuits to direct the operation of image and 
raster generation circuits and to control the input/output of power 
supply operation.  
The SCB sets the operating parameters of the image, such as 
brightness and contrast. It also produces internal test patterns and 
generates on-screen display overlays. The SCB sets the timing for 
the raster generation to adjust phase, geometric corrections, 
shading corrections, and convergence. The program memory and 
the memory for all convergence and shading maps are located on 
the SCB. 
The following functions are performed or controlled by the System 
Controller: 
• Enables control for the Low Voltage Power Supply, Arc Lamp 
and cooling fans. 
• Fault monitors the HVPS, LVPS, Arc Lamp, and fans. 
• Provides interboard communication via the IIC serial bus. 
• Controls Zoom and Focus of the Projection Lens. 
• IIC Interface control 
• Provides Video Overlays 
• X and Y convergence control 
• Threshold and Sensitivity for shading 
• I/O control 
• Two RS-232 serial interface ports 
• Infrared (IR) remote control interface. Accepts input from front 
or rear IR detectors. 
• A 5-wire JTAG interface port for CPU emulation support. 
• External 3 color system status LEDs. Green indicates normal, 
yellow is standby and red indicates a fault condition. 
• External Service Mode switch (see Figure 5-1). Pressing this 
switch during a power-up sequence brings the system up in a 
diagnostic mode (for maintenance) rather than a normal 
operating mode. 
The SCB I/O diagram (Figure 2-12) and the list of Inputs and 
Outputs (Table 2-9) provide information for the technician to 
perform module-level troubleshooting. 
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							Chapter 2---System Description 
P11
B23B24
B28B29
B32
B27
B26
B31B30
Lens ZoomLens Focus
/LV_ENA/FAN_ENA
/LAMP_ENA
/HV_OK
/LV_OK
/LAMP_LIT/LAMP_OK
P10B31B30A32A31A30
A   B20-2021-2122-2223-2324-2425-2526-2627-2728-2829-29
+5.1V stby
+5.1V
+15V-15VGND
ODD_FIELD
SRC_VALIDH_DRIVE_SCV_DRIVE
B9B10B2B1B3
RED_OVER
GRN_OVER
BLU_OVER
B18B17
B16
P10
Y_RED_CONVY_GRN_CONVY_BLU_CONVX_RED_CONVX_GRN_CONVX_BLU_CONV
B4B5B6B1B2B3
BLU_THRESGRN_THRESRED_THRESBLU_SENSGRN_SENSRED_SENS
B8B9B10B11B12B13
IIC_DATA
IIC_CLK1IIC_CLK
IIC_CLK3IIC_CLK2
SYSTEM
CONTROLLER
BOARD
TO PROJLENS
FROMLVPS
FROMHVPS
FROMALPS
FROMRTG
FROMLVPS
TOVPB
TOCDB
TOVPB
H_F2V
 
Figure 2-12.  System Controller Board, Block Diagram.  
IIC Interface 
Communications are performed through the IIC bus to the other 
PCBs in the system.This three wire bus interface consists of clock 
line, data line and interrupt line. Data transferred over the IIC bus 
is listed in Table 2-9 (I/O signals). 
System Controller Board Input/Output  
This section provides a description of the inputs to and outputs 
from the SCB. The I/O descriptions are arranged by the 
source/destination of the signal. The format used is such that the 
assembly communicated with is used as the primary heading of 
each output. Input refers to an input to the SCB, output refers to 
an output from the SCB. 
 
Table 2-9.  System Controller Board I/O signals 
Video Processor Board
I/O DESCRIPTION 
IIC_CLK IIC clock line. Clock line for control of synchronous data transfer over\
 
the IIC bus interface. 
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							  Chapter 2---System Description 
IIC_DATA IIC data line. Serial line for synchronous data transfer of the followin\
g 
data between Video Processor Board and SCB board. I=Input, 
O=Output. 
I     BEAM CURRENT 
I     OK DETECT 
O    RED_CONT 
O    GRN_CONT 
O    BLU_CONT 
O    BRIGHTNESS 
O    RED_G2 
O    BLU_G2 
O    GRN_G2 
O    WHT_BOOST 
O    BLK_BOOST 
 
OUTPUTS DESCRIPTION 
OVERLAY Overlay control signal 
/IIC_INT IIC interrupt line.  
RED_OVER Red signal of on-screen menu and/or internal test pattern 
GRN_OVER Similar to RED_OVER 
BLU_OVER Similar to RED_OVER 
BLU_THRES Threshold correction information for blue. Real time data at 0 volt to 
1 volt. 
GRN_THRES Similar to BLU_THRES 
RED_THRES Similar to BLU_THRES 
BLU_SENS Sensitivity correction information for BLU. Real time data at O volt to \
1 volt. 
GRN_SENS Similar to BLU_SENS 
RED_SENS Similar to BLU_SENS 
Raster Timing Generator
INPUTS DESCRIPTION 
SOURCE_ 
VALID 
This signal indicates a new source (or valid). A high indicates a vali\
d 
stable signal and low indicates change in input signal. 
ODD_FIELD Square wave with 50 % duty cycle which is low during the odd field 
of an interlace signal. This signal is high for noninterlaced signals. 
280_CLK Square wave signal, 50 % duty cycle, 280 times the frequency of 
horizontal sync. This clock is synchronized to the horizontal sync. 
2-36 Model 200 Service Manual