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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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Compaq MV740 Model: Co1056u
Hello, just posting a solution to a monitor problem.
Symptoms: No picture and power/standby light seems to operate nomally. Problem: Surface mount capacitor connected to pin 8 of U702(LM2437T) on Daughter board has shorted out. Thus overloading the 12v line and causing the SMPS to shut down. Now I didn't have a schematic nor was I able to get a reading off of the original device. So I measured one similar in size and it read about 1nf. R715(3.3ohm carbon film) takes a beating and may have burned the board. Replace if nessessary. Also take a look at Q812 on the mainboard. It may have been damaged too. |
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On Sat, 30 Oct 2004 23:21:40 GMT, "Jim" put
finger to keyboard and composed: Hello, just posting a solution to a monitor problem. Symptoms: No picture and power/standby light seems to operate nomally. Problem: Surface mount capacitor connected to pin 8 of U702(LM2437T) on Daughter board has shorted out. Thus overloading the 12v line and causing the SMPS to shut down. Now I didn't have a schematic nor was I able to get a reading off of the original device. So I measured one similar in size and it read about 1nf. 1nF appears too low, unless there are bigger caps elsewhere on the same rail. See the application circuit in this datasheet: http://cache.national.com/ds/LM/LM2437.pdf R715(3.3ohm carbon film) takes a beating and may have burned the board. Replace if nessessary. Also take a look at Q812 on the mainboard. It may have been damaged too. - Franc Zabkar -- Please remove one 's' from my address when replying by email. |
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