Text preview for : ATC311_Dig_Align04m.pdf part of Chasis ATC221
Back to : ATC221.rar | Home
Understanding Digital Convergence and Geometry
ATC311 / 221 and ITC222 Chassis
Contents
Understanding Convergence / Geometry Alignment ................ 4 ATC311 ....................................................................................... 4 ATC221 and ITC222 .................................................................. 4 Alignment Overview (ATC311)...................................................... 5 Key Points of Manual Alignment .................................................. 5 Going Through the Geometry Process ...................................... 5 Convergence.................................................................................. 7 ATC221 Alignment Overview ........................................................ 8 Alignment After Green CRT Replacement ................................. 10 Red or Blue CRT Replacement ................................................... 11
Understanding Convergence / Geometry Alignment Convergence and geometry alignments in the digital chassis work together in producing the best possible picture from a projection TV. In the past there was room for error and the picture would be ok. Today, convergence and geometry work closely together and if one is off it can mean a poor converged picture or auto-convergence not working. In order to do the convergence alignments one needs to fully understand geometry, convergence and the different display modes (2H and 2.14H). To start off with the display modes are the frequency at which horizontal is operating. For example 2H is twice the NTSC horizontal frequency of 15.750kHz or 31.5kHz and 2.14H is 15.750kHz times 2.14 or 33.7kHz. In addition to the 2H and 2.14H display modes there are signal modes 480i, 480p 1080i, 540p, and 720p. The p and i stand for the type of scanning, progressive or interlace. ATC311 The ATC311 will receive 480i, 540p, 720p, and 1080i but will only display 480p and 1080i, hence the 2H (480p) and the 2.14H (1080i) modes. This means that the ATC311 needs to convert the other signals to on of these two scan modes. The conversion processes is done in the DM2 module so that the 480i will be up-converted to 480p display and the 720p is converted to 1080i. There are three ways of providing signals to the chassis: 1. Component (YPrPb) 2. Digital (DVI) 3. NTSC inputs When using the component YPrPb input, the signal can be NTSC (1H), 2H, or 2.14H. The DM2 detects the horizontal frequency of the incoming signal and determines which one of two paths the signal will take. It will either be converted or processed directly for display. The only signal processed directly for display is the 1080i all others are sent to the DM2 for conversion. ATC221 and ITC222 Through out this publication the ATC221 will be discussed and related to both the ATC221 and ITC222 chassis. The ITC222 will be used only when there is a difference from the ATC221. The ACT221 and ITC222 are HDTV monitors and use the same signals as the ATC311 for their alignments. Monitor indicates there is no internal ATSC tuner for HD reception. These sets are capable of displaying HD just not processing the ATSC signals. Because of this, the ATC221 and ITC222 require an external signal (generator) for the 2.14H display.
It is Thomson's recommendation that a generator capable of all necessary signals (480p to 1080i) be used when doing geometry and convergence alignments. Even if it is possible to receive the signals via off-air / cable, a generator is recommended.
Page 4
Alignment Overview (ATC311) Before doing any alignments you need a good understanding of what will be done, the type of test equipment, and what the results of the alignments are. This information can be found by reading the entire alignment process before starting the actual alignments. It is this step that will result in a good experience or a bad one when doing alignments. Keeping that in mind, most sets today have both manual and computer alignment modes. The ATC311 can be aligned using the latest version of Chipper Check or by using the service man alignment mode. The service man menu is for touch up alignments. If parts are replaced such as the deflection CBA or CRT's then Chipper Check will be needed to do the complete alignments. As mentioned earlier, the ATC311 has two scan modes: 480p and 1080i. When doing geometry alignments the 480p mode should be done first and then the 1080i. This is important as the values found during the 480p mode are used for the 1080i adjustments. If they are not correct then both modes will be off and proper alignment can't be achieved. This could result in auto convergence not working or overdriving the convergence amplifiers resulting in over heating the convergence outputs. Tech-Tip: If a generator is not available, the signals from the DM2 in the ATC311 can be used. Keep in mind the signals tuned to must be the standard 480i and 1080i signals. This will be displayed on the info bar of the OSD. The 480i signal is up-converted to 2H by the DM2. KEY Points of Manual Alignment First and for most, geometry needs to be correct before even considering convergence alignment. If geometry is not correct auto-convergence may not work. This cannot be stressed enough "good geometry equals good convergence". Using the service data Alignment Procedures read the entire Geometry Adjustments first before actually doing the alignments. This will give you a good understanding of what to do and when it needs to be done. Also make sure you have a good working generator capable of providing the necessary signals required to do all the alignments. This is important if your generator is not able to supply all signals used then you wont be able to complete the alignment process. You should also be familiar with your generators operation. The generator is used for sync purposes only and the internally generated crosshatch pattern is used as the reference pattern. This pattern is used for both convergence and geometry. Tech-Tip: Use the generator crosshatch to aid in geometry alignment only. Use the Internally generated convergence pattern to verify proper alignment. This requires jumping back and forth between the convergence and geometry alignments. Going through the Geometry process: Step 1: Input a 2H (480p) crosshatch signal using the component input. This signal is used for sync only. Use the internally generated convergence pattern for proper geometry alignment. This requires jumping back and forth from geometry to convergence. Step 2: Reset picture controls This step sets the brightness and color controls to default values for easier viewing by the technician. Page 5
Step 4: Set P7 to V63 Step 5: Set P8 to V16 Step 6: Set P9 to V16 Steps 4-6 are starting points for these parameters. They will be re-adjusted after vertical size is properly set. Step 7: Adjust P11 for 7.5% over-scan When viewing the internally generated convergence pattern there are half boxes around the outer edges. When adjusting for 7.5% over scan this equates to the top and bottom half squares being pushed off the screen and ¼ of the next box or ¾ of a whole box.
Internally generated convergence pattern
Internally generated convergence pattern after 7.5% over scan adjustment
7.5% Over Scan (Not Visiable)
Outer Screen Frame
Step 8: Adjust P6 to obtain straight vertical lines Step 9: Adjust P8 and P9 to straighten the top and bottom lines. Steps 8 and 9 straighten the vertical lines to the screen frame. Another way of determining the straightness is by attaching a weight to the end of a string and suspending it from the top of the screen frame. This will create a plumb line that can be used to determine the straightness of the vertical lines (Make sure the set is sitting level). This should be placed over the second fully visible line in from the edge of the screen. Step 10: Repeat steps 7-9 getting the corners as straight as possible. Step 11: Adjust P4 to center the picture horizontally. Page 6
Again using the internally generated convergence pattern at P80, adjust for internally generated convergence pattern to be centered in the screen frame. Step 12: Record the final values for P5, P6, P7, P8, P9, and P11. These values will be used to setup the 480i up-converted NTSC parameters in the EEPROM. These parameters are not adjusted just copied when in the 480i mode. Step 13: Exit the service menu to store the new values. Pushing the power button stores the values and exits the service menu. The above steps are repeated using a 1080i-generated signal for the 2.14H HDTV mode geometry alignment. The only difference is do not set the vertical size to 7.5% over scan. Set the internally generated convergence pattern just inside the screen frame as in the following picture.
Convergence After geometry is correct, convergence can be done. Like geometry, convergence needs to be done in each mode (480p and 1080i). NOTE: Doing the convergence is time consuming so allow your self plenty of time to do the alignments correctly. This is where making a mistake could cause the entire process to be started over. It is recommended that each color (Red and Blue) be adjusted and saved independently of each other. In other words do the red adjustment save it and then do the blue and save it. This will minimize lost data if a mistake is made. Before starting the convergence alignment access the service menu 80 and toggle through till only green is displayed. Green must be straight and centered before the other colors can be converged. Remember green is what the other colors are aligned to so if green is off so will the other colors. Here are a few tricks, when doing convergence that can be helpful. · Look at the entire screen and determine the best path to align each color. Keep in mind the interaction between points. Although small with digital convergence there is still some interaction. · When doing the individual points focus on the center of the cross first then the legs. This will help line-up several points in a row that need to be adjusted. · Work from the center of the screen outward. Page 7
· ·
Start at the most out of convergence point and work towards the least. This works for lines that are bowed start in the center of the bow and work to the ends. Use the points that are off the screen. Visually look at the outer edges and using your imagination, adjust these points. This is very important when adjusting when the pattern is over-scanned the 7.5% for 480p mode.
After convergence is done and saved, parameter 82 is accessed. Parameter 82 is an automatic process that locates and saves the sensor position. This process looks the same as auto-convergence but during this process each sensor around the screen is located and the exact position is memorized for auto-convergence operation. If the process is successful, a green block will appear on the screen. A red block indicates a sensor position was not located and auto convergence won't work. NOTE: This typically happens when geometry is not correct. ATC221 Alignment Overview The ATC221 and ITC222 are similar in their alignment processes. Reading each process before doing any alignments will result in proper alignment. As with the ATC311 using the proper equipment is critical. The ATC221 and ITC222 up-convert the 480i signal but need a generated 1080i signal for alignments. Doing geometry alignments are slightly different for the ATC221 and ITC222 verses the ATC311. When doing the alignments for the ATC311 we used the internally generated convergence pattern for proper alignment. When doing the alignments on the ATC221 and ITC222 we use generated test patterns and the internally generated internally generated convergence pattern. However, the end goal is the same, proper geometry equals autoconvergence working. As with the ATC311 there are different modes 480i and 1080i. When doing the alignments both modes need to be adjusted for proper operation of the unit. Only doing the 480i mode will result in auto-convergence not working and a possible call back from the customer. Going through the Geometry process: NOTE: These adjustments will be performed using external generated patterns and the internal convergence generated pattern. When using the internal convergence generated pattern, this requires the technician to exit the geometry adjustment screen and enter the convergence adjustment screen. This pattern is used for reference only and no adjustments are to be made in the convergence menu when adjusting geometry. Step 1: Place instrument in the Field Service Mode. (Follow procedures in service data) Step 2: Enter the Tube submenu and make sure the correct tube type is entered. Step 3: Tune the instrument to receive a crosshatch pattern. It is not necessary to exit the service menu to change channels. At any point in the service menu if you press clear on the remote it will take you back to normal TV operation. To go back to the service menu, simply hold the menu button down on the remote for 5 seconds and the service menu will be brought back up. Step 4: Return to the Geometry submenu Page 8
Step 5: Adjust the V-slope (Vertical Slope) until the middle line of the test pattern is just visible. This adjustment is not available for the ITC222 when tuned to 1080 signal. Step 6: Exit the service menu and turn the instrument off. Disconnect the convergence correction yoke connectors (BW001 and BW002). Turn the instrument back on and tune to receive a centerline pattern. Adjust horizontal and vertical centerlines according to the chart found in the service data using the static centering magnets. When completed turn the instrument off and reconnect BW001 and BW002. The chart is found on page 3-5 of the service data "Alignments". Figure 2 on page 36 shows how to rotate the centering rings. This chart provides Red and Blue off set information for all screen sizes. Step 7: Place instrument in the Field Service Mode. Make sure the instrument is receiving a Mono-scope pattern. If not, clear out of the service menu and tune to a Mono-scope pattern. Using the mono-scope pattern, adjust V-Amplitude (Vertical Amplitude) until the first and last horizontal line of the pattern is just hidden by the screen frame. This step sets the vertical size of the displayed picture. Step 8: Adjust V-Position (Vertical Position) until the mono-scope pattern is centered vertically. Step 9: Adjust V-Linearity (Vertical Linearity) for equal height of the squares in the crosshatch pattern. NOTE: Step 7, 8, and 9 may need to be repeated till the internally generated convergence pattern is correctly positioned inside the screen frame. Step 10: Adjust H-position (Horizontal Position) until the internally generated convergence pattern is horizontally centered. Step 11: Using a Mono-scope pattern adjust the H-Amplitude (Horizontal Size) until the first and last horizontal lines of the pattern are hidden by the screen frame. Check using the internally generated convergence pattern to make sure the pattern is with in the screen frame as indicated in the figure below.
Internally generated convergence pattern inside Screen Frame
Step 12: Using a crosshatch pattern adjust EW-Amplitude (East West Amplitude) until the vertical lines in the middle of the screen are straight. Step 13: Adjust EW-Trapezium (East West Trapezium) for best compromise between left and right vertical lines. Page 9
What we are looking for here is that the first and second vertical lines in from the sides are straight. This is best done using a string connected at the top and bottom forming a visual reference line. Just make sure your string is straight. Step 14: Adjust EW-Symmetry (East West Symmetry) until the left and right borders are the same. NOTE: Steps 10-14 may need to be repeated until the internally generated convergence pattern is properly adjusted. Also check by accessing auto-convergence, if it won't run then geometry is not properly set.
Alignment After Green CRT Replacement In doing any alignment first read and understand the alignment process found in the service data. This procedure will help you get started when the green CRT needs to be replaced. Sense green is the main or center color, all others are aligned to green. This can make setup of the green CRT critical. The first and most important step in replacing the green CRT is to mount the new one as close as possible to where the old one was. There are several tricks to doing this like, marking the exact position of the old tube before removing it, using reference points as alignment marks, and taking good quality picture(s) of the assembly before the tube is replaced. Next is making sure the yoke and ring assemblies are properly placed on the replacement CRT. Remember that the components off the old tube have been digitally aligned with this set. This will minimize the electrical alignments needed if they are placed at the same spot on the new tube as they were on the old one. There is only one trick in getting the replacement tube close to the old one and that is measure the distance and location of each component. Tech Tip: When marking the new tube for component replacement set both tubes face down on a level table. Using a 4' level and a sharpie make a mark for the placement of each component. All components should be marked before removing any. Once the green CRT is mounted, allow the set to warm up for 20 minutes and access the convergence pattern (P80 for ATC311). Adjust the green centering rings till the green convergence pattern is aligned to the blue and red patterns. This should be done looking at the overall pattern not just the center. After centering rings are set go ahead and run autoconvergence. This should bring the green in to convergence. If the green is not aligned then do minor adjustments using the convergence alignment process in the service data or using Chipper Check (ATC311 only). If auto-convergence won't complete the centering or geometry is off. Make sure that it failed on the green. If green failed then the centering was not properly set for green. If it failed on red or blue, geometry is more than likely off. Page 10
Red or Blue CRT Replacement Replacement of the red or blue CRT is easier than replacement of the green. As mentioned in the green CRT replacement, make sure the components from the old CRT are properly placed on the replacement. When replacing the red or blue CRT adjust the centering rings to align with the green pattern. Once centered, access auto-convergence. Running auto-convergence should align the red and blue with the green. If auto-convergence won't complete the centering or geometry is off. Make sure what color it failed on. If red or blue failed then the centering was not properly set. If it failed on green, then geometry is more than likely off. Tech Tip: The sensor detection process requires all three colors to be detected by each sensor in order to complete the process. It will stop on the first sensor it cannot detect. By watching closely one can determine what color and sensor it stopped on. This can be very helpful in alignment diagnoses. For example say it stopped on the green upper right hand corner, this would indicate that centering or horizontal phase is not properly set for the green. In other words the picture needs to be shifted to the left.
Page 11