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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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Toshiba Rear Projection Convergence board problem
Hey,
I had a post about a problem with a rear projection 24KHz RGB monitor from a Waverunner arcade game (old topic was "50" Mitsubishi Rear Projection Help"). Anyway, after looking at it, I noticed that it's actually a Toshiba, but I'm unsure of the model (it's missing the back panel where the model number should be). I'm starting a new topic as the original problem appears to be solved, and this is more of a specific problem now. I had problems with the monitor not staying on, and it ended up being a problem with the convergence board. I found an opened resistor at the -15V line on the convergence board, which is a 2 ohm (appears to be a 1W) resistor. I don't have an exact replacement, but I have lots of other low value resistors, which I hooked up to get within the 5% allowed of the original resistor. Anyway, now it comes up, but the convergence is WAY off. This model has no manual pot adjustments, so I guess I have to adjust it all through the menu. I do have the remote, but it doesn't seem to be allowing me to change any of the convergence manually. It'll let me change size and position, but when I follow the instructions for adjusting convergence that I found online, it just sits there doing nothing. You can see a pic of how bad it is he http://dogp.home.comcast.net/waverunner/DSCF0741.JPG and a picture of the convergence board he http://dogp.home.comcast.net/waverunner/DSCF0745.JPG and a picture of the chassis he http://dogp.home.comcast.net/waverunner/DSCF0671.JPG and: http://dogp.home.comcast.net/waverunner/DSCF0672.JPG I also pulled the convergence adjustment pages out of the manual and they can be found he http://dogp.home.comcast.net/waverunner/convergence.pdf , in case any of you guys recognize the adjustment procedure from other Toshibas, and have seen a similar problem. Does anyone know why when I hit the adjust buttons, nothing happens? Would it be something with the new resistor I put in, or would something else be blown, or is there some sort of protect switch or something? Searching the internet for Toshiba convergence problems seems to pull up a lot about the output transistors on the convergence board, would that make it unadjustable and way out of adjustment, and would it seem possible that all three colors are not adjustable? So far, I've tested all large transistors on the convergence board, and none are shorted, and I've tested the outputs of the remote, and they're good. Any other ideas of what to check? Thanks, Pat |
#2
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Toshiba Rear Projection Convergence board problem
Don't adjust the convergence until you repair the convergence
circuitry. It will be way out of wack, when you later realize it was bad in the first place. Replace the STK...-...convergence IC's. The resistor is propably blown again. Also check all the low ohmage resistors. After repairing the convergence, you can "tweak" it if need be. Sky. "DogP" wrote in message ups.com... Hey, I had a post about a problem with a rear projection 24KHz RGB monitor from a Waverunner arcade game (old topic was "50" Mitsubishi Rear Projection Help"). Anyway, after looking at it, I noticed that it's actually a Toshiba, but I'm unsure of the model (it's missing the back panel where the model number should be). I'm starting a new topic as the original problem appears to be solved, and this is more of a specific problem now. I had problems with the monitor not staying on, and it ended up being a problem with the convergence board. I found an opened resistor at the -15V line on the convergence board, which is a 2 ohm (appears to be a 1W) resistor. I don't have an exact replacement, but I have lots of other low value resistors, which I hooked up to get within the 5% allowed of the original resistor. Anyway, now it comes up, but the convergence is WAY off. This model has no manual pot adjustments, so I guess I have to adjust it all through the menu. I do have the remote, but it doesn't seem to be allowing me to change any of the convergence manually. It'll let me change size and position, but when I follow the instructions for adjusting convergence that I found online, it just sits there doing nothing. You can see a pic of how bad it is he http://dogp.home.comcast.net/waverunner/DSCF0741.JPG and a picture of the convergence board he http://dogp.home.comcast.net/waverunner/DSCF0745.JPG and a picture of the chassis he http://dogp.home.comcast.net/waverunner/DSCF0671.JPG and: http://dogp.home.comcast.net/waverunner/DSCF0672.JPG I also pulled the convergence adjustment pages out of the manual and they can be found he http://dogp.home.comcast.net/waverunner/convergence.pdf , in case any of you guys recognize the adjustment procedure from other Toshibas, and have seen a similar problem. Does anyone know why when I hit the adjust buttons, nothing happens? Would it be something with the new resistor I put in, or would something else be blown, or is there some sort of protect switch or something? Searching the internet for Toshiba convergence problems seems to pull up a lot about the output transistors on the convergence board, would that make it unadjustable and way out of adjustment, and would it seem possible that all three colors are not adjustable? So far, I've tested all large transistors on the convergence board, and none are shorted, and I've tested the outputs of the remote, and they're good. Any other ideas of what to check? Thanks, Pat |
#3
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Toshiba Rear Projection Convergence board problem
Thanks, I'll replace those STK ICs... I wasn't sure if it was actually
not adjusting, or if it was trying to adjust and there was just a problem with the board. I did test all of the low ohm resistors, and the one I replaced is the only one that was bad... and it hasn't blown again yet, but it's also higher wattage than the other was. Pat |
#4
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Toshiba Rear Projection Convergence board problem
DogP wrote: Hey, I had a post about a problem with a rear projection 24KHz RGB monitor from a Waverunner arcade game (old topic was "50" Mitsubishi Rear Projection Help"). Anyway, after looking at it, I noticed that it's actually a Toshiba, but I'm unsure of the model (it's missing the back panel where the model number should be). I'm starting a new topic as the original problem appears to be solved, and this is more of a specific problem now. snip Does anyone know why when I hit the adjust buttons, nothing happens? Would it be something with the new resistor I put in, or would something else be blown, or is there some sort of protect switch or something? Searching the internet for Toshiba convergence problems seems to pull up a lot about the output transistors on the convergence board, would that make it unadjustable and way out of adjustment, and would it seem possible that all three colors are not adjustable? So far, I've tested all large transistors on the convergence board, and none are shorted, and I've tested the outputs of the remote, and they're good. Any other ideas of what to check? Thanks, Pat Hi Pat, This is a special 15-24Khz (CGA-EGA) Toshiba Monitor built for Video Arcade Games I looked long and hard in our company archives and files for the schematics but it looks like Toshiba never gave out copies when we purchased these. Start File Notes Toshiba 50" Rear Projector Engine Model No:P-R502L PCBs VIDEO/CONV PB6101 HOZ/FLY PB6105 CONV-OUT PB6112-1 POWER PB6106 IC Information Sanyo STK392-020 3-channel convergence correction amplifier (2pcs per monitor) HOD Tr 1MB12-140 INSULATED GATE BIPOLAR TRANSISTOR Fuji Electric To enter convergence mode. Note: You need to have a working Game Raster input first 1/- Switch front panel convergence switch to on 2/- Press and hold TEST button for 5 seconds until convergence screen is up 3/- MODE switches between - Center Convergence - Line Convergence - Point Convergence 4/- the four POSITION keys select what to adjust in Line & Point Convergence Modes 5/- the four ADJUST keys will move the current selected Convergence Mode 6/- the three keys R, G & B select and toggle on/off each color 7/- SELECT will switch between Game Raster input and Convergence Test 8/- NEVER-EVER press the RESET key.. all stored convergence data will be deleted from memory and you will have a horrible time just to get the screen all squared up again. 9/- The WRITING key writes the current convergence data to memory. Do this often as any power glitch can exit you from convergence mode and you will loose all current settings you have made. Convergence Tips 1/- Use Green as your base color. 2/- Square up the green grid 3/- use the point convergence to make all the vertical and horizontal lines straight as possible. 4/- For Red & Blue, first use Center convergence to converge the center of the screen, Red-to-Green & Blue-to-Green. 5/- Then Square up each color to match the green, Red-to-Green & Blue-o- Green. 6/- Finally use Point Convergence to get best overall convergence, Red- to-Green & Blue-to-Green. End File Notes Your photos look like all the convergence data has be reset or lost so you have a long job in front of you. I don't think that the convergence amps are bad as all three guns are giving similar shaped pictures. Bad Convergence amps usually show up as one or two colors badly or unevenly distorted. I start with Green only and use black electrical tape across the monitor front evenly spaced to the number of vertical and horizontal grid lines. Start with the horizontal first then the vertical. Once you have a good green square grid, then adjust the other colors to match. Wes. |
#5
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Toshiba Rear Projection Convergence board problem
Wes,
Thanks a lot, that helps a TON! I pulled the board out to check for the STK ICs, and I noticed that there aren't any on this board (it's all discrete transistors). So just for fun, I started testing the resistors again, and I noticed that the resistor I pulled was supposed to be a 0.2 ohm, and I replaced it with a 2 ohm _. I must have put a decimal point in the wrong place or something... I always mess up some mundane detail ;-). Anyway, I did have an extra 0.2 ohm resistor from another arcade monitor, so I popped that in, and it looked a LOT better, and best of all, it's adjustable! Of course Sky was right, all of the "adjustments" that I was trying to make when it wouldn't adjust were saved, and those needed to be adjusted back, and tonight I'll take your advice on getting the convergence looking perfect, and then hopefully this thing will be looking and playing great! :-) Thanks again for all the help guys! Pat |
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