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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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I have an IBM Thinkpad A20m laptop (2628-4UU) that failed last evening
with the same symptoms that literally hundreds of others have reported over the last few years. Mine had been running fine, but I went to power it up and, once it got to the Windows desktop it froze. Powered off, then tried powering on again. Unit comes on when power is pressed (HD spins up, all lights flash on then go off except for power, I can hear the CPU fan running). No POST, no boot, black screen. I replaced the CMOS battery, reseated everything, yada yada yada. The thinkpads.com web forums list a possible cause as a failure of one (or both) chips in the dc-dc power section on the mainboard. These are the Analog Devices ADP3421JRU and ADP3410KRU ICs. This is supposedly due to a design flaw. Some people also say to change three MOSFETs (IRF-7811) as well. Some report success, others don't. It seems to me that by simply replacing the chips you're not fixing the problem. SOMETHING caused the chips to fail as there wasn't (to my knowledge, anyway) a bad run of those chips. Bad capacitors in the circuit, maybe? Bad resistors, diodes ...? People ARE apparently fixing the boards, as dealers will sell you refurbished ones or will fix your broken unit. So, what's the secret? Which components are routinely replaced during the course of one of these repair jobs? ** To respond, remove the crap from my addy... ** |
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