Hughes JVC Projector 250 Service Manual
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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 receives a power OFF command, the /LAMP_LIT and the /LAMP_ENA signal both go high. This shuts off the Arc Lamp Power Supply. The /FAN_ENA signal stays low for an additional ten minutes allowing the cooling fans to cool down the Arc Lamp, the Light Pipe and the PCBs. After ten minutes, the /FAN_ENA signal goes high, shutting off the cooling fans.
Chapter 7---Troubleshooting 7-14 Model 250 Service Manual 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. The separated image and sync signals go to the Video Processor PCB. In the Video Processor PCB the image signals are modified with Brightness, Contrast, Gamma Correction, Sensitivity and Threshold. The modified image signals go to the Video Amplifier PCB where they are go through an amplifier and on to the CRTs. The horizontal and vertical sync pulses are routed to the Raster Timing Generator PCB. In the case of Sync-on- Green type sync pulses, the horizontal and vertical syncs are stripped from the green image signal in the Video Processor PCB.
Chapter 7---Troubleshooting Model 250 Service Manual 7-15 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 generates the horizontal deflection sawtooth waveform. The Raster Timing Generator PCB divides the range of horizontal scan frequencies into four groups or bands because the retrace or flyback timing varies dramatically from the lowest frequency (15 kHz) to the highest frequency (90 kHz). The Horizontal Vertical Deflection PCB generates the horizontal waveforms that drive the CRT Yokes. Many of the geometric corrections are integrated into the horizontal waveform at the Horizontal Vertical Deflection PCB such as Pincushion, Keystone, Skew, and Bow. The vertical size is be adjusted on the Horizontal Vertical Deflection PCB.
Chapter 7---Troubleshooting 7-16 Model 250 Service Manual 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 Generator PCB (V_DRIVE) signal and generates a sawtooth waveform ( V_RAMP). It sends this signal to the Vertical Amplifier on the Horizontal Vertical Deflection PCB. It also sends geometric correction to modulate the vertical deflection waveform (V_PARAB) to the Horizontal Vertical Deflection PCB. The Convergence Deflection PCB sends convergence correction data received from the System Controller PCB to the Scan Reversal PCB (X_RED+, GRN+, and BLU+) and (Y_RED+, GRN+, and BLU+). The convergence correction data goes from the Scan Reversal PCB to the Convergence Yokes on each CRTs. The Scan Reversal PCB sends the horizontal and vertical deflection waveforms to the appropriate CRT. It also converts the waveform for floor/ceiling and front/rear projector installations.
Chapter 7---Troubleshooting Model 250 Service Manual 7-17 Figure 7-13 CRT Deflection path between Horiz/Vert Deflection PCB, Convergence Deflection PCB and Scan Reversal PCB.
Chapter 7---Troubleshooting 7-18 Model 250 Service Manual Figure 7-14 CRT Deflection path between the Scan Reversal PCB and CRT.
Chapter 7---Troubleshooting Model 250 Service Manual 7-19 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 excessive beam current that may damage the CRT. Deflection Waveform Detection The CRT Protection circuit protects the CRTs by monitoring the deflection waveforms in two different ways. On the Scan Reversal PCB, there is a H_SENS and V_SENS signal for each CRT. These sense lines detect the presence of the horizontal and vertical deflection waveforms. The horizontal and vertical sense lines for each CRT combine into a RED, GRN, or BLU_DEFL_OK signal (see Figure 7-16). These RED, GRN, or BLU_DEFL_OK signals combine into one DEFL_OK signal that goes back to the Horizontal Vertical Deflection PCB. On the Horizontal Vertical Deflection PCB, the DEFL_OK (normally high and the /H-ENA (normally low) go into an NOR logic gate with an inverted input for the H-ENA signal. The /H_ENA signal shuts down the horizontal amplifier during changes in source input. If DEFL_OK goes low or /H_ENA goes high, the output /SWEEP_OK goes high. If the /SWEEP_OK signal, on the Video Amplifier PCB, goes high, the G 1 supply and the G2 Regulator circuit shut down. On the Video
Chapter 7---Troubleshooting 7-20 Model 250 Service Manual 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 also goes to the Video Processor PCB where a logical “high” shuts down the G 2 control voltages. Yoke Connector Detection The CRT Protection circuit also ensures that CRT Yoke connectors are properly installed. It does this with the H_LOCK+/- circuit. This series circuit goes from the Horizontal Vertical Deflection PCB to the Scan Reversal PCB, through each CRT Yoke connector, and back to the Horizontal Vertical Deflection PCB. The H_LOCK+ has +15 V applied to it on the Horizontal Vertical Deflection PCB. If all the CRT Yoke connectors are properly installed H-LOCK+ and H_LOCK- will both measure +5 V. If the any one of the connectors is not properly installed, H_LOCK+ will measure +15 V and H_LOCK- will measure 0 V. If H_LOCK- is at 0 V. This shuts down the horizontal amplifier circuit that generates the horizontal deflection waveform. CRT Beam Current Another function the CRT Protection circuit performs is to monitor the beam current of each CRT. The Video Amplifier PCB outputs a current sense line (RED, GRN, and BLU BEAM) from each image amplifier circuits. The Video Processor PCB receives these current sense lines and compares them to a reference. If the beam current of any CRT exceeds 250 µ A, the Beam current LED illuminates orange, and the Video Processor PCB reduces Contrast. If reducing Contrast does not bring the CRT beam current below 250 µ A, the Video Processor PCB reduces the G 2 voltage until the beam current drops below the limit.
Chapter 7---Troubleshooting Model 250 Service Manual 7-21 Figure 7-16 CRT Protection path between the Scan Reversal PCB and CRT.
Chapter 7---Troubleshooting 7-22 Model 250 Service Manual 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 Convergence/Deflection PCB, Horizontal/Vertical Deflection PCB, Raster Timing Generator PCB, Video Amplifier PCB, Video Processor PCB. 4 POWER ON/OFF Power On Sequencing. 5 FLASH MANAGER Flash Memory Data Manager. 6 VIDEO SWITCHER EXTRON or JVC Video Switcher Handler. 7 ANSI OUTPUT ANSI Output Display process. 8 UI CHAN/SRC User Interface VIC Configuration Handler for Channel/SRC Data. 9 VIDEO INPUT CARD VIC Card Handler. 10 HARDWARE Misc HW (shutters, etc.). The error codes listed in Table 7-2 describe problems associated with software (Version 2.6.0) and hardware while the projector is operating. The first column of the table lists the error number code that appears on the PC screen. The second column describes the on-screen text. The third column provides a description of the problem and any other pertinent information. Table 7-2 Error Codes. Error NumberOn-Screen Text Description 1.5 “Invalid read/wrt” Software error-mismatch. Open mode vs. Write or Read command. 1.12 “Ser parity error” Serial Port Parity error-not currently used. 1.13 “Bad dev I/O oper” Software error-invalid I/O request. 1.27 “Timeout on Read” Software error-unexpected timeout on Read.