Learning motherboard repair - Page 1
Forum section: electronics / beginners

author: SolderOcelot
author_rank: Contributor
timestamp: November 13, 2019, 03:14:50 pm
content: Why this topic?I've been wanting to learn computer motherboard repair for over 1.5 years. You would think there is plenty of resources out there but Istronglydisagree. I've learned so much by my self on the internet (cooking, coding how to do a double windsor tie knot) but when it comes to computer motherboard repairs, I find that Louis Rossman, iPad rehab and even Sorin jump right in the middle and don't really consider beginners.What's the device?It's an old Lenovo laptop with a faulty motherboard. I can replace the motherboard for $ 38 but that's not the point of this project.Model:Lenovo x220Motherboard part number:48.4kh17.021FactsSymptoms: No power, no boot, no charging ledCharger has been checked and replacedDC jack has been replacedDC jack connector on motherboard has been measured with multimeterIn the past (while the mobo was still faulty) I have been able to get the motherboard to power and boot laying bare like this (with just keyboard and hdmi cable attached)CPU gets warm when motherboard is connected to DC jack for over 5 to 10 minutesQuestionWhat's the sensible next component to check without using schematics and why?Shouldn't I have 20.5V on the black to ground point where I have 0V now?Please bear in mind I'm an electronics beginner and so extra info on your comment is appreciated.

author: tszaboo
author_rank: Super Contributor
timestamp: November 13, 2019, 03:20:10 pm
content: Check all the fuses. That PCB looks damaged, maybe try to clean it and see if it is in one piece or charred and dead.

author: SolderOcelot
author_rank: Contributor
timestamp: November 13, 2019, 03:22:04 pm
content: Quote from: NANDBlog on November 13, 2019, 03:20:10 pmThank you. I've cleaned it with IPA multiple times and since it powered on before after I played with it for hours, I have a feeling the PCB isn't broken / damaged.Good point on the fuse.

author: Jan Audio
author_rank: Frequent Contributor
timestamp: November 13, 2019, 05:12:10 pm
content: Put in oven after removing all plastic.

author: SolderOcelot
author_rank: Contributor
timestamp: November 13, 2019, 08:12:14 pm
content: Quote from: Jan Audio on November 13, 2019, 05:12:10 pmThanks, what spices should I add?

author: GreyWoolfe
author_rank: Unknown
timestamp: November 13, 2019, 10:36:30 pm
content: Quote from: Faloude on November 13, 2019, 08:12:14 pmCoriander. I like coriander.

author: george.b
author_rank: Frequent Contributor
timestamp: November 13, 2019, 11:50:39 pm
content: Everything is easier to repair when you have the schematics. I think the ones for the X220 are available around the internet. Get them.Next, check all power rails. Zeroth rule of troubleshooting: "thou shalt check voltages". Many (if not most) problems can be solved this way.If the rails are okay, well, then you gotta put your thinking cap on and work your way from whatever signs of life (if any) the motherboard gives, which might involve probing around to find out what is going on (and what isn't). Probing clocks is a reasonable next step.Keep in mind you can't always win - replacing, say, a toast BGA chip, unless you have the necessary equipment, will probably cost much more than a replacement motherboard.A perhaps more-to-the-point ThinkPad repair anecdote of mine: I once repaired a T400 that was seemingly dead. The problem was a shorted USB port. IIRC, the USB power chip was toast as well. Replacing both USB port and USB power chip brought the board back to life. No fuses were blown by the short or anything.Another thing that comes to mind: Some ThinkPads will misbehave when the CMOS battery is depleted. Check that.

author: pcmad
author_rank: Regular Contributor
timestamp: December 06, 2019, 12:03:09 am
content: does any compounts get hot after it been pluged in for some time look there