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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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#1
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CTX 1451ES raster but no pic
I'm repairing this old monitor just because I don't wanna throw it away.
Strange symptoms, has HV, heater, and if I turn up the G2, a perfectly normal looking raster, however there's no image at all when connected to a known good source. Anyone seen this one? |
#2
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Does it have an LM1203(n) RGB processor IC (look close to where the VGA
cable terminates, it's a big 24 or 28 pin package, physically similar in dimensions to old 27xxx EPROMs)? If so, these blow regularly. Also, if it has a 74(LS/HC/etc)08 IC biffering the sync signals from the VGA cable (follow Hsync & Vsync path), these also blow regularly. Otherwise, follow the RGB colour signals with a CRO, and see where they get lost. "James Sweet" wrote in message news:FQled.510$LT1.179@trnddc09... I'm repairing this old monitor just because I don't wanna throw it away. Strange symptoms, has HV, heater, and if I turn up the G2, a perfectly normal looking raster, however there's no image at all when connected to a known good source. Anyone seen this one? |
#3
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"Craig Hart" wrote in message ... Does it have an LM1203(n) RGB processor IC (look close to where the VGA cable terminates, it's a big 24 or 28 pin package, physically similar in dimensions to old 27xxx EPROMs)? If so, these blow regularly. It has a M51387P IC buffering the RGB signals, so far as I can tell this is the culprit. Vcc is ok, varying voltages present at the RGB inputs, zero on all three outputs. Anyone have one of these in a scrap monitor before I order a new one? |
#4
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I would check the voltage on the contrast pin of the M51387P.
Many IC's run near 4 volts on this pin. I would try connecting a low voltage adjustable power supply to this pin and change the voltage and see if that brings the video back. I have had a couple of monitors where I had to add a resistor between a voltage source on the board and the contrast pin in order to supply the proper voltage and get a good video. Hope this helps.... John "James Sweet" wrote in message news:xZSed.3859$8R.1050@trnddc02... It has a M51387P IC buffering the RGB signals, so far as I can tell this is the culprit. Vcc is ok, varying voltages present at the RGB inputs, zero on all three outputs. Anyone have one of these in a scrap monitor before I order a new one? |
#5
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IIRC I got about 5.6v at the contrast pin, are you saying I should see
around 4v? Does voltage higher raise or lower contrast? "John Gill" wrote in message om... I would check the voltage on the contrast pin of the M51387P. Many IC's run near 4 volts on this pin. I would try connecting a low voltage adjustable power supply to this pin and change the voltage and see if that brings the video back. I have had a couple of monitors where I had to add a resistor between a voltage source on the board and the contrast pin in order to supply the proper voltage and get a good video. Hope this helps.... John "James Sweet" wrote in message news:xZSed.3859$8R.1050@trnddc02... It has a M51387P IC buffering the RGB signals, so far as I can tell this is the culprit. Vcc is ok, varying voltages present at the RGB inputs, zero on all three outputs. Anyone have one of these in a scrap monitor before I order a new one? |
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