ASUS N73JF not powering on after freeze spray - Page 1
Forum section: electronics / repair

author: martyr
author_rank: Newbie
timestamp: March 24, 2017, 05:52:52 pm
content: Hello everyone,I am new around here and this is my first post. And this is going to be very noob oneIt's Asus N73JF Rev 2.1 motherboard. I don't know what went wrong but it's all happened while swapping a new HDD into laptop.Whole thing started after i install a new HDD. I was upgrading to SSD. Everything was working perfect until i upgrade to SSD.I went into bios to change boot order to install new OS to new SSD, after saving BIOS and rebooting its never skipped bios logo and i was unable to go into bios again. I have tried everything before disassembling laptop.So i have disassembled to make sure there's nothing wrong with external hardware or daughterboards. I did a visual inspection but there was no visible damage. I have removed anything and tried to boot (even without screen).But there was no change at all.Anyway, i have tested some components with multimeter and found out that there is a short circuit on motherboard.My multimeter was set to "continuity" mode. I've realized that, caps are that near to the CPU were in short circuit.After doing more research, i tought that freeze spray might help to detect any failing components.I have applied freeze spray to components and tried to power on with adapter (it's 19V 4.5A) and then everything messed up.There is no visual damage, no smell or something.Now when i power on the motherboard, CPU fan tries to "wake up" but it's not spinning at all. Power LED turns on for 1 sec and its turning off.Appearently, i did awful job with freeze spray and i believe i have caused more damage.Folks, please keep in mind that my goal is the fixing it by myself and gaining experience. It's not a a matter of life and death for me. I am just trying to figure out what went wrong and what is the right approach to troubleshoot such case. Plus, i am always looking ways to improve myself and gain some experience.Right now, i can read 3.3v, 5v and 19V on motherboard. So seems like there are still alive components CPU gets very hot, i don't know if such high temperature is normal without a proper boot and OS load.I have a basic multimeter, soldering equipment and half bottle of freeze spray.Is it worth to keep working on it? Or should i send this mobo to trash?What are the proper methods/approaches to start troubleshooting from my current state?To be honest, i am not sure how and where to get started with laptop repairing. I have just near-to-basic electronics knowledge. Where should i get started?Thanks in advance!

author: Johncanfield
author_rank: Regular Contributor
timestamp: March 24, 2017, 08:59:35 pm
content: You are at a huge disadvantage without a scope.

author: Messtechniker
author_rank: Frequent Contributor
timestamp: March 25, 2017, 10:52:30 am
content: The first thing to do with misbehaving motherboards is:Check or better replace the BIOS battery first.Some motherboards do extremely weird things with a flat battery.The second thing to do is visually check the motherboard (and the power supply, if external to the motherboard) for electrolytic capacitors blowing their top and replace any of these.Further visual inspection as to any chips, resistors or connectors with burn marks.Step. No. 3. Measure the voltages on the motherboard making sure they are within tolerance.After this you are on your own.Further troubleshooting aids you may initially need:A thermal camera may help to verify spots which should be either hot or cold.Some kind of magnification (lens or camera) to detect broken or burnt pcb. tracks.A DMM with a low resistance range (milli Ohms) to detect any excessively high contact resistance in connectors.

author: Rasz
author_rank: Super Contributor
timestamp: March 25, 2017, 03:12:03 pm
content: asus -> trashyou didnt detect short, CPU has VERY low internal resistance and thats why your meter beeped, plus you said laptop was still powering on and displaying logo.My guess would be spraying near weakened cpu power section made something crack from induced thermal shock, if cpu is boiling you might have shorted power section now = fried cpu.its first gen i3, whole working laptop is ~$60.

author: tpowell1830
author_rank: Frequent Contributor
timestamp: March 25, 2017, 03:44:40 pm
content: Hi martyr, welcome to the forum.Since you changed out HD, I would start there by removing new HD and put old one back in. Inspect connector for bent pins and shorts, etc. Sometimes, we have found the problem, and the problem is us.

author: martyr
author_rank: Newbie
timestamp: March 25, 2017, 08:27:06 pm
content: Hello everyone,Thanks for amazing tips and help.@MesstechnikerI have replaced BIOS battery, nothing changed.Visual inspection is also good, i can't see any burn or cracked spots.Voltage measurements looks good, except CPU section of the board. (i guess)I think it thermal imaging would be very expensive, right?@RaszYes i think you are right. It wasn't a "short". I thought it was a short due to lack of my knowledge. Maybe it wasn't shorted at all...And yes, i agree on your guess on spraying. Obviously spraying killed some components.But i can't say CPU is boiling. All i am saying (or asking), is that normal to have that regular temperature on CPU even without boot and BIOS?Just trying to understand if CPU gets hotter even without proper boot and BIOS loading. So i can distinguish if i killed CPU or not.@tpowell1830I have tried with several HDDs but also i have removed daughterboard of SATA controller. So i think this problem is far beyond of HDD issue.

author: martyr
author_rank: Newbie
timestamp: March 25, 2017, 09:38:01 pm
content: Just a quick add, now i got the boardview file of the board.Does it help at all?How i should use this? I mean, i am able to open file with board viewer software.Which points i should measure first?

author: pishta
author_rank: Contributor
timestamp: March 27, 2017, 02:32:04 am
content: Does mobo have a "supercapacitor" chip on it? I had 2 Toshiba laptops given to me that had bad SC chips that I replaced and used for years after that. Its a large black SMD mount chip with no visible pins. Hard to replace without a reflow station but I managed with a heat gun and some foil mask...

author: martyr
author_rank: Newbie
timestamp: March 27, 2017, 02:41:55 pm
content: Attached mobo pics and my measurements

author: Kim_555
author_rank: Contributor
timestamp: March 27, 2017, 08:32:19 pm
content: Hello.Do not worry, you did not cause any damage to the friezer. You need an oscilloscope for qualitative diagnostics. I attach the schema and program to view to the message. You will be able to check the voltage which should be lifted after pressing the button. You will need to extract each *.rar archive, and then get the files from it.

author: Kim_555
author_rank: Contributor
timestamp: March 27, 2017, 08:33:42 pm
content: You also need to check how the BIOS is read after the power is connected and the button is pressed. Perhaps the reason for this is that the bios settings are not correct and the laptop does not turn on.I also attach the BIOS dump, which must be programmed by the programmer. Downloaded by the programmer from a working laptop Asus N73JF MAIN BOARD REV:2.1.Ask if you need to.In my video you can see how the BIOS should read from a chip, and as it can be seen on an oscilloscope. On this video, a laptop with a similar problem - does not turn on. Video on Russian, but hopefully it will help you understand how to solve a problem.https://youtu.be/dRnARVQbpPo