Notebook Repair - does not power up immediately after usage  - Page 1
Forum section: electronics / repair

author: solderfun
author_rank: Newbie
timestamp: August 09, 2021, 12:51:25 pm
content: Lenovo 3000 N200 4GB RAMOld Lenovo Notebook (non Thinkpad).Worked fine for more than 10 years. Then there was an overheating issue I guess.So I added an external Papst fan to help me.Worked."Weird" Behaviour:After I turned off the notebook, there was basically no chance to start it immediately again, even if the notebook worked for 12 hours to copy files without any issues.After waiting some longer period time of time (hours) it would eventually turn on again.Externally cooling could not convince the notebook to turn on faster / immediately.First "analysis":As the notebook works for hours copying files, the basic function of CPU/RAM/Interfaces must be ok.So there must be an issue with the built in / external power supply.Guessing:There must be a part maybe a "fuse" of some "protective circuit" of some sort, which may recover after some time?Some parts of power circuit may not provide power to CPU etc..Any ideas greatly appreciated.Danke / Thank You / Bedankt / Merci

author: amyk
author_rank: Super Contributor
timestamp: August 09, 2021, 01:41:41 pm
content: Check discharge MOSFETs.Your model is OEM Compal, either LA-3451p or LA-3571p. Check mobo for the exact part number. Schematic should be easily obtained based on that.

author: solderfun
author_rank: Newbie
timestamp: August 10, 2021, 12:56:07 pm
content: What a downgrade from a Thinkpad.Mech construction "interesting".Its a 3451p. Pages 39++ show DCIN / CHARGER / ....Must be somewhere around here?There are lots (7+) of MOSFETs.NO experience with this kinda stuff, but non destructive soldering is ok.BTW, NO Battery connected.POWER LED turns on and can be turned off.Thanks.

author: amyk
author_rank: Super Contributor
timestamp: August 10, 2021, 01:36:02 pm
content: Page 3 has the power rail usage and page 35 has the discharge MOSFETs (lower right corner). According to the table, all of those rails should be at 0V if the unit is not running. Check which ones still have voltage with it turned off (use a high impedance DMM, this will mainly be only residual charge.) Alternatively, you can disconnect AC and battery, then short each of those rails to ground briefly to discharge them, and see if the unit can turn on immediately after that. This will confirm whether it is a discharge problem.

author: solderfun
author_rank: Newbie
timestamp: September 07, 2021, 10:35:08 am
content: Again. Thanks a lot. Good experience on the forum with this funny weird problem.I was able to transfer data from encrypted drive running old software on computer. Took ages as computer took forever to decrypt.The construction really flimsy and I am scared to ruin it by taking it completely apart.Therefore I have not managed to to go on with the the proposed solution regarding the discharge MOSFETs, as this problem suddenly did not persist as I changed something else.KICKING stupid fan control!Fan control weird!If CPU is cold and heats up even to excessive temp, then fan control does not bother at all to engage.But if CPU was totally overheated when turning on, then suddenly I get fan spin for the whole session, even temp is below threshold after some time.WTF.So overheat CPU first, then reboot, to brutally cool it down agin? Not a good idea for long CPU lifetime I guess.Fan controller must have issue, so I went to turn on fan continuously right from start. Just by shorting reverse voltage discharge diode.Works just fine. Computer louder, but works for the purpose much safer and more reliable. Happy. Hack, I know.