[SOLVED]Dell motherboard (LA-910aP) no power troubleshooting - Page 1
Forum section: electronics / repair

author: dominicM
author_rank: Regular Contributor
timestamp: July 14, 2017, 01:25:50 pm
content: I have a dell LA-910aP motherboard with no signs of life. It was liquid damaged. I get 19V on the DCIn and even 19V, 5V and 3V on the battery controller (PU100). I cant seem to find where the issue lies. It's difficult to trace as there is no pcb layout available. What is the likely cause? What would be fists things to check? What are the logical steps to take to attempt to find the issue? There is no power draw at the wall and no voltage beyond the dcin area as afar as I can tell. Same with or without battery. No visible damage after liquid cleaned. Any suggestions or tips appreciated.Datasheet:http://kythuatphancung.vn/uploads/download/b2f74_Compal_LA-9104P_VAW00_Inspiron_3521.pdf

author: wraper
author_rank: Unknown
timestamp: July 14, 2017, 01:36:46 pm
content: Quote from: dominicM on July 14, 2017, 01:25:50 pmWith liquid damage it could be basically anything.

author: Armadillo
author_rank: Super Contributor
timestamp: July 14, 2017, 01:46:58 pm
content: The liquid may be salty conductive, wash, scrub again and dry again.

author: dominicM
author_rank: Regular Contributor
timestamp: July 14, 2017, 01:56:23 pm
content: I realise water damage can damage almost any part of the motherboard but wouldn't the fact that there is no power past a certain point narrow the cause a little? Aren't some components more or less likely to to fail in this manner than others? I already did wash with distilled water prior to asking but issue is exactly the same as before. If something is conductive wouldn't it normally cause short-circuits? To me it would seem to narrow any bridges so certain components but I don't know specifically which ones.

author: Armadillo
author_rank: Super Contributor
timestamp: July 14, 2017, 02:02:10 pm
content: Quote from: dominicM on July 14, 2017, 01:56:23 pmExample reset Pin, if the voltage don't rise to a start up level, the micro don't even start and appeared completed dead.Or protection circuit activated etc... layer of conductive salt cannot be wash by just distilled water. What kind of water damaged is that? soda, coke ?Plug in a POST diagnostic card.

author: dominicM
author_rank: Regular Contributor
timestamp: July 14, 2017, 02:09:03 pm
content: Quote from: Armadillo on July 14, 2017, 02:02:10 pmThis is a laptop so no PCI slot. There is also no power on most of the motherboard so it wouldn't work anyways. I only get voltage around dcin and battery controller. There is also no voltage on the power button pcb connector.+Not sure what liquid it was, could be soda, beer or something like it.

author: Armadillo
author_rank: Super Contributor
timestamp: July 14, 2017, 02:30:21 pm
content: Quote from: dominicM on July 14, 2017, 02:09:03 pmThere are the mini PCI-E bus, the LPC bus etc...See picture.

author: dominicM
author_rank: Regular Contributor
timestamp: July 14, 2017, 02:41:18 pm
content: Quote from: Armadillo on July 14, 2017, 02:30:21 pmTrue but like I said it's no use as there is no voltage apart from close to dcin and no voltage at the power on button and you can't have POST when power on button is not functional.

author: Armadillo
author_rank: Super Contributor
timestamp: July 14, 2017, 03:03:02 pm
content: You can find the shorts by using a thermal imager.Maybe some can advise you the feel method.

author: Rbastler
author_rank: Frequent Contributor
timestamp: July 14, 2017, 03:04:55 pm
content: Or pour alcohol over the various parts of the circuit, and look for the component, where it evaporates the quickest.

author: dominicM
author_rank: Regular Contributor
timestamp: July 14, 2017, 03:11:32 pm
content: Quote from: Armadillo on July 14, 2017, 03:03:02 pmLike I already said there is no short circuit, there is ZERO power draw from a power supply.

author: khaahk
author_rank: Contributor
timestamp: July 14, 2017, 05:31:07 pm
content: PU100 needs to get DCIN, ACIN should be logical high,PQ100 and 101 should be opened to let adapter voltage to B+PU200 should get give REF VREG3 and VREG5 when EN is logical highKBC needs to have 3.3 ALW power on pin 9,22 etc.and KB9012 needs to be externally programmed if changed on this mainboard.

author: dominicM
author_rank: Regular Contributor
timestamp: March 30, 2018, 12:04:01 pm
content: Quote from: khaahk on July 14, 2017, 05:31:07 pmI came back to this eventually and followed your suggestions. It turned out to be PU200. VIN pad was corroded, running a wire fixed the issue. Thank you!