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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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IBM P70 Monitor (Sony GDM-17SE2T variant) horizontal size problem.
G'day folks, I have an IBM P70 (Type 6554-674) that no matter what
display mode I choose, (640*480 - 1600*1280), it always has approx. 30-35mm of each side of the screen unused when the horizontal size is adjusted to %100. Vertical size is fully adjustable to the viewable area limits. I've tried different computers, (including one that will allow me to set vert/horiz. frequencies other than the standard, the full range that the monitor is capable of), and it still will not allow a full width picture. If I turn up the brightness sufficiently I can see the raster edges end approx 20-25mm from the edges of the viewable area, with the output display ending approx 15mm short of that, if you know what I mean. The output display is fully positional within the raster area. Crappy ASCII pic follows, (haven't bothered showing top/bottom): Screen edge Screen edge v v | 20 |15| |15| 20 | | mm |mm| Display |mm| mm | | | | output | | | ^ ^ Raster edge Raster edge Would this possibly be because of reduced horizontal drive? I have a Service Manual for the GDM-17SE2T, (has some minor control differences), but before I got into the guts of the thing I was wondering if anyone had any ideas? TIA, Dave |
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IBM P70 Monitor (Sony GDM-17SE2T variant) horizontal size problem.
Dave:
I have had some experience with this problem on Dell/Sony GDM-17SE2T monitors. Behind the flyback, there is a small transformer in location T403. Mine had the number 998-11 on it. These transformers develop small cracks in the core that is on the outside of the windings. This somehow affects the horizontal width. I had two monitors with narrow widths. Replacing the transformers with ones from junked chassis fixed the problem. There is also another transformer in location T701. This one can develop cracks too, but it controls the dynamic focus. You can have good focus in the center, but be out-of-focus on the edges, or vise-vera. Hope this helps... John |
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IBM P70 Monitor (Sony GDM-17SE2T variant) horizontal size problem.
John Gill wrote:
Dave: I have had some experience with this problem on Dell/Sony GDM-17SE2T monitors. Behind the flyback, there is a small transformer in location T403. Mine had the number 998-11 on it. These transformers develop small cracks in the core that is on the outside of the windings. This somehow affects the horizontal width. I had two monitors with narrow widths. Replacing the transformers with ones from junked chassis fixed the problem. Thanks John, I'd just put the D board into service position and was about to check the B+ and associated items mentioned in Sam's Repair FAQ. This will give me something else to look for, it might even be the real cause, (ruling out caps, etc), since the width does not vary with temperature, (just ~50mm too small). There is also another transformer in location T701. This one can develop cracks too, but it controls the dynamic focus. You can have good focus in the center, but be out-of-focus on the edges, or vise-vera. Focus seems to be OK so far, though of course it hasn't gone to full width yet. Hope this helps... John Thanks again, Dave |
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IBM P70 Monitor (Sony GDM-17SE2T variant) horizontal size problem.
John Gill wrote:
Dave: I have had some experience with this problem on Dell/Sony GDM-17SE2T monitors. Behind the flyback, there is a small transformer in location T403. Mine had the number 998-11 on it. These transformers develop small cracks in the core that is on the outside of the windings. This somehow affects the horizontal width. I had two monitors with narrow widths. Replacing the transformers with ones from junked chassis fixed the problem. Just a followup John, after checking the voltages and finding them spot-on, I pulled T403 and had a good look at it - sure enough a small crack. When I eased off the tape around it a section of the core dropped off. So thank you very, very much for sharing this with me, (and the rest of us), this would have saved me hours checking resistors, ESR on caps, etc. I only hope I can get a replacement now, (either the whole thing or poss. the cores). Thanks again, Dave |
#5
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IBM P70 Monitor (Sony GDM-17SE2T variant) horizontal size problem.
John Gill wrote:
Dave: I have had some experience with this problem on Dell/Sony GDM-17SE2T monitors. Behind the flyback, there is a small transformer in location T403. Mine had the number 998-11 on it. These transformers develop small cracks in the core that is on the outside of the windings. This somehow affects the horizontal width. I had two monitors with narrow widths. Replacing the transformers with ones from junked chassis fixed the problem. ARRGGHHH!! I had high hopes for this but unfortunately replacing the relevant T403, (which had a cracked core), hasn't resolved the problem - the raster is still 50-60mm too narrow, so back to the drawing board. Dave |
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