Hughes JVC Projector 250 Service Manual
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Chapter 5---Electronics 5-16 Model 250 Service Manual 6. Pull the black card extractor handles back to disconnect the Video Processor PCB connector and pull the PCB out of the Electronics Module. 7. Reverse the procedure to install the Video Processor PCB. 5.5 Raster Timing Generator PCB Raster Timing Generator PCB - Main Functions ! Generates an internal sync pulse ! Detects and selects sync pulses ! Generates a phase locked sync ! Generates blanking pulse ! Provides horizontal and vertical phase adjustments ! Detects interlaced and generates odd field pulse ! Selects horizontal frequency band ! Generates horizontal line count and vertical count ! Provides IIC interface ! Generates clamp pulse ! Detects changes in source ! Generates HVPS_SYNC signal ! Enables horizontal deflection (/H_ENA) circuitry Figure 5-10 Raster Timing Generator I/O diagram for Power Supplies.
Chapter 5---Electronics Model 250 Service Manual 5-17 Figure 5-11 Raster Timing Generator for other PCBs. Raster Timing Generator PCB - Inputs V_SYNC - input vertical sync from the Video Processor PCB. H_SYNC - input horizontal sync from the Video Processor PCB. G_SYNC - Sync-on-Green sync stripped from green video signal at the Video Processor PCB. ISYNC - 5 MHz clock from the System Controller PCB used to generate the internal sync.
Chapter 5---Electronics 5-18 Model 250 Service Manual IIC_CLK - IIC clock line. Unidirectional clock line for control of synchronous data transfer over the IIC bus. IIC_DATA - IIC data line. Bi-directional serial line for synchronous data transfer between System Controller PCB and Raster Timing Generator PCB. +15 V (two inputs) - input power from LVPS for analog circuitry including the Phase Lock Loop (PLL) circuit. -15 V (two inputs) - input power from LVPS for analog circuitry including the Phase Lock Loop (PLL) circuit. +5.1 V - input power from the LVPS for digital circuitry Raster Timing Generator PCB - Outputs SOURCE_VALID - signal to the System Controller PCB, indicates a new or valid source. High = valid, stable source, low = change in input source. ODD_FIELD - square wave to System Controller PCB, with 50% duty cycle that is high during the odd field of an interlaced signal and low for non-interlaced signals. 280_CLK - square wave to System Controller PCB, with 50% duty cycle, synchronized to the horizontal sync at 280 times the frequency of the horizontal sync. This signal is used by the System Controller PCB to properly output shading and convergence data. CLAMP - a negative-going image clamp signal to the Video Processor PCB, with about 3% duty cycle. BLANKING - right, left, top, and bottom blanking signal to the Video Processor PCB. H_BAND(0-3) - horizontal frequency band lines to the Horizontal Vertical Deflection PCB. Band 0 = 15 - 24 kHz Band 1 = 24 - 28 kHz Band 2 = 28 - 55 kHz Band 3 = 56 - 90 kHz /H_ENA - enables the horizontal deflection amplifier on the Horizontal Vertical Deflection PCB, Low = enabled deflection; high = disabled deflection. H_FV2 - a DC voltage to the Horizontal Vertical Deflection PCB and System Controller PCB, proportional to horizontal frequency. H_DRIVE - square wave to the Horizontal Vertical Deflection PCB, 50% duty cycle synchronized to the selected horizontal sync. This signal provides a sample of the horizontal sync to the horizontal amplifier on the Horizontal Vertical Deflection PCB. HVPS_SYNC - synchronization pulse for High Voltage Power Supply, synchronized with the selected horizontal sync at the same, half, or one third the frequency.
Chapter 5---Electronics Model 250 Service Manual 5-19 V_DRIVE - square wave negative going pulse to the Convergence Deflection PCB, synchronized to the selected vertical sync with the pulse width of about four horizontal periods. Raster Timing Generator PCB - Operation The Raster Timing Generator PCB generates a square wave that is phase-locked to the horizontal sync pulse. It generates timing signals such as Blanking that goes to the Video Processor PCB and Video Amplifier PCB, and the H_DRIVE signal that goes to the Horizontal Vertical Deflection PCB. The PLL (Phase Locked Loop) locks these signals to the horizontal sync signal. The Raster Timing Generator PCB has LEDs that indicate the type of sync pulse received and the status of the PLL circuit (see Figure 5-12). The H_DRIVE signal supplies a sample of the horizontal scan frequency to the horizontal deflection amplifier on the Horizontal Vertical Deflection PCB for timing of the horizontal deflection waveform. The Raster Timing Generator PCB checks the incoming syncs to make sure they are valid signals and within the frequency ranges (15 - 90 kHz - horizontal, and 45 - 120 Hz vertical). If the syncs are out of range, or there is no sync pulse, the Raster Timing Generator PCB generates an internal interlaced sync at 33.7 kHz horizontal and 60 Hz vertical. The Raster Timing Generator PCB tells the System Controller PCB when there has been a source change using the SOURCE_VALID signal. The Raster Timing Generator PCB generates the Blanking signal, and the horizontal Phase signal. ! Blanking shuts off the image during times where there is no active video. The Blanking signal pulls the G1 voltage on the Video Amplifier PCB down far enough to make the CRT shut off. The Raster Timing Generator PCB receives the top, bottom, left, or right blanking command on the IIC bus and sends the appropriate Blanking signal to the Video Processor PCB. The Raster Timing Generator PCB receives the Blanking adjustment commands on the IIC bus. ! The horizontal Phase signal adjusts the on-screen image horizontally to compensate for different phase requirements at different horizontal scan frequencies. The Raster Timing Generator PCB receives this command from the System Controller PCB on the IIC bus. The Raster Timing Generator PCB sends several signals such as 280_CLOCK signal to the System Controller PCB to correctly set the timing for shading and convergence data. In order to combat noise caused by crosstalk between supplies (beat patterns) the High Voltage Power Supply is phase locked to the incoming horizontal frequency by the HVPS_SYNC signal. The horizontal flyback time gets shorter as the horizontal scan frequency increases. The Raster Timing Generator PCB works together with the Horizontal
Chapter 5---Electronics 5-20 Model 250 Service Manual Vertical Deflection PCB to break the range of horizontal scan frequencies into four smaller ranges called bands (see Figure 5-12). Figure 5-12 LEDs on the Raster Timing Generator PCB. Raster Timing Generator PCB - Remove and Replace Tools Needed #1 Pozi-drive Phillips-head screwdriver Parts Needed Raster Timing Generator PCB - p/n 105238 To remove the Raster Timing Generator PCB: 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. Disconnect all the external source video cables and control cables. 4. Remove the rear cover. 5. Remove the Back Panel. Remove the nine Pozi-drive Phillips-head retaining screws using the #1 Pozi-drive Phillips screwdriver. 6. Pull the black Card Extractor handles back to disconnect the Raster Timing Generator PCB connector and pull the PCB out of the Electronics Module. 7. Reverse the procedure to install the Raster Timing Generator PCB.
Chapter 5---Electronics Model 250 Service Manual 5-21 5.6 Horizontal Vertical Deflection PCB Horizontal Vertical Deflection PCB - Main Functions ! Drive the main horizontal deflection coils to provide horizontal raster scan for the CRTs ! Drive main vertical coils to provide vertical raster scan for the CRTs ! Horizontal raster centering for all three colors ! Switch mode power supply generating the required proportional DC supply ! Horizontal width adjustment ! Horizontal retrace switch network ! Left/right pincushion and keystone correction ! Vertical linearity adjustments individually for all three colors. ! Vertical raster centering for all three colors ! IIC interface. Horizontal Vertical Deflection PCB - Inputs H_BAND:0-3 - horizontal scan frequency bands, from Raster Timing Generator PCB. /H_ENABLE - from the Raster Timing Generator PCB, enables the horizontal deflection supply. Low = enabled deflection, High = disabled deflection. H_DRIVE - square wave from the Raster Timing Generator PCB, 50% duty cycle synchronized to the selected horizontal sync. H_F2V - a DC voltage from the Raster Timing Generator PCB, proportional to horizontal frequency H_LOCK (neg.) - Deflection Yoke Connector Interlock return from the Scan Reversal PCB. DEFL_OK - deflection status signal from the Scan Reversal PCB (high = good, (about 2 V), low = no scan). V_RAMP - vertical ramp waveform from the Convergence Deflection PCB, (about 4 Vpp). V_PARAB - vertical parabola waveform from the Convergence Deflection PCB, (about 4 Vpp). FRONT/REAR - front or rear projection status line from the Scan Reversal PCB. (FRONT = low, REAR = high). FLOOR/CEILING - floor or ceiling projection status line from the Scan Reversal PCB. (FLOOR = low, CEILING = high).
Chapter 5---Electronics 5-22 Model 250 Service Manual IIC_CLK - IIC clock line IIC_DATA - IIC data line IIC_SINT - IIC interrupt ±15 V - input power from the Low Voltage Power Supply, for the analog circuitry. +5.1 V - input power from the Low Voltage Power Supply, for the digital circuitry. Figure 5-13 Horizontal/Vertical I/O Diagram.
Chapter 5---Electronics Model 250 Service Manual 5-23 Figure 5-14 Horizontal/Vertical I/O Diagram for Scan Reversal and Video Amplifier PCBs.
Chapter 5---Electronics 5-24 Model 250 Service Manual Figure 5-15 Physical layout of the Horizontal/Vertical PCB (note the Vertical Size Adjustment Pots (Red-137, Grn-148, and Blu-160) on the lower right). Horizontal Vertical Deflection PCB - Outputs /SWEEP_OK - signal to the Video Amplifier PCB, derived from the H_ENA signal from the Raster Timing Generator PCB, and the DEFL_OK from the Scan Reversal PCB. WIDTH_CTRL - a DC voltage to the Convergence Deflection PCB that adjusts the parabola waveforms used for geometric correction (about 4 V max.). H_RGB(pos.) - horizontal deflection waveform return from the Scan Reversal PCB. A DC offset that shifts the reference for red, green, and blue image for centering. H_OUT_FLYB - output waveform to the Scan Reversal PCB for the horizontal deflection coils on the CRTs. H_LOCK (pos.) - +15 V to the Scan Reversal PCB for deflection yoke connector interlock. V_RGB (pos.) - positive vertical deflection voltage to the Scan Reversal PCB. V_RGB (neg.) - negative vertical deflection voltage to Scan Reversal PCB. ±15 V - pass through voltage from Low Voltage Power Supply to Scan Reversal PCB to power analog circuitry. +5.1 V - pass through voltage from Low Voltage Power Supply to Scan Reversal PCB to power digital circuitry. H_CUR_FDBK - current feedback to horizontal waveform amplifier.Vertical Adjustment Pots
Chapter 5---Electronics Model 250 Service Manual 5-25 Horizontal Vertical Deflection PCB - Operation The Horizontal Vertical Deflection PCB consists of a RGB horizontal deflection amplifier and separate vertical deflection amplifiers. The Horizontal Deflection Amplifier The horizontal deflection amplifier is a switching mode power supply that varies according to the input horizontal sync frequency. The horizontal supply generates the sawtooth current-driven waveform that drives the horizontal deflection coils on the CRT. The sawtooth current waveform creates the raster on the CRT. The horizontal amplifier also generates the retrace waveform portion of the raster. The horizontal deflection sawtooth waveform is modulated by other waveforms that perform geometric correction such as Pincushion, Keystone, Horizontal Centering, Horizontal Linearity and Horizontal Width adjustment. The Width Control voltage also goes to the Convergence Deflection PCB to adjust the geometric correction parabolas. The H_F2V signal converts the input horizontal scan frequency to a voltage that switches from one band (see explanation of bands in the Raster Timing Generator PCB Operation section) to the next depending on the horizontal scan frequency. This adjusts the retrace time to correspond to the input horizontal frequency. The output of the horizontal supply is H_OUT_SUPPLY that goes on to the Scan Reversal PCB. CRT Protection The Horizontal Vertical Deflection PCB uses the H_LOCK+, H_LOCK- and DEFL_OK signal to protect the CRTs from being damaged if the deflection waveforms are lost. Refer to the CRT Protection section in Chapter 9 for a complete discussion of these and all the signals associated with CRT Protection. The Horizontal Vertical Deflection PCB receives the DEFL_OK signal from the Scan Reversal PCB indicating the presence of the horizontal and vertical deflection waveforms. If there is a failure of any of the Deflection Yokes (horizontal or vertical), a current sense line on the Scan Reversal PCB forces DEFL_OK low. On the Horizontal Vertical Deflection PCB, the DEFL_OK signal becomes /SWEEP_OK and is sent to the Video Amplifier PCB where it shuts down G 1. If DEFL_Ok is forced low, or if /H_ENA is forced high, /SWEEP_OK goes high. The /SWEEP_OK goes to the Video Amplifier PCB. If it goes high, it shuts down the G 1 voltages and G2 Regulator circuit (see Troubleshooting, CRT Protection section). Vertical Deflection Amplifier The vertical deflection sawtooth waveform is generated on the Convergence Deflection PCB and timed to the vertical sync by the V_DRIVE signal from the Raster Timing Generator PCB. The Convergence Deflection PCB sends this waveform along with a parabola waveform V_PARAB to the vertical deflection amplifier on the Horizontal Vertical Deflection PCB. The Horizontal Vertical Deflection PCB takes V_RAMP, amplifies it and adds geometric correction with