Replacement for power mosfet on PC motherboard help. - Page 1
Forum section: electronics / repair

author: mnm972
author_rank: Newbie
timestamp: May 22, 2016, 08:52:41 am
content: Hello,I have Dell 390 pc and it has problems booting, blinking amber light.From the manuals from dell and online, I understood that its power or mobo problems.I have checked the PSU and it's ok.When I examined the motherboard I have noticed bad caps, Replaced them and still have amber blinking light.I saw the the 12V, 4 pin was shortening, so I have started checking and found the mosfet.I have found this one which has short, and I want to replace it.part number is:09N03LA GAK643See attached pic.I could not find it online with full serial only this one.How do I know if it's N-Channel or P-Channel?Is this okhttp://eu.mouser.com/ProductDetail/Infineon-Technologies/IPD09N03LA-G/?qs=%2fha2pyFadujKqCbGM5FKNCyta3qQ1s358bSg3yOPapYxz6OaMs84MyNeYFlWgT00? what important values should I check when replacing power mosfet? e.g in caps ESR, Voltage, Temp..Would something like this be OK?http://www.ebay.com/itm/10-PCS-ME70N03A-TO-252-ME70N03-30V-N-Channel-Enhancement-Mode-MOSFET-/371086608611?hash=item56667c48e3:g:CUUAAOxyGwNTBcP~Thanks!

author: PA0PBZ
author_rank: Super Contributor
timestamp: May 22, 2016, 10:27:00 am
content: http://lmgtfy.com/?q=09N03

author: Whales
author_rank: Super Contributor
timestamp: May 22, 2016, 11:06:35 am
content: Beware that desoldering that part will be a PITA. It's right on a large solid-fill copper area and motherboards tend to suck more heat than a black hole.

author: mnm972
author_rank: Newbie
timestamp: May 22, 2016, 12:05:09 pm
content: Quote from: Whales on May 22, 2016, 11:06:35 amThanks Whales,How do you suggest to desoldar it, with what technique,I don't have hot gun.Is this mosfet N-channel or P-Channel?Is the replacment part I linked will fit?

author: viswesh
author_rank: Newbie
timestamp: May 22, 2016, 12:32:21 pm
content: according to datasheet it is N-channel MOSFET, the part number itself tells 09N03L N is for channel.. i think it is okaythank you.

author: mnm972
author_rank: Newbie
timestamp: May 22, 2016, 04:39:12 pm
content: Quote from: viswesh on May 22, 2016, 12:32:21 pmThanks viswesh,You are right, I checked in the datasheets and it is N channel, I think the part is IPD09N03LA GPackage is P-TO252-3-11 but I don't know the voltage, I guess I can use higher than original (> 20 will be ok, no?).I plan to desolder it with iron and wick, any recommendation about it?Thanks!

author: botcrusher
author_rank: Regular Contributor
timestamp: May 22, 2016, 05:06:44 pm
content: Careful, i wouldn't go about making substitutions on MOSFETs when there are others in parallel. Use the same model, CPUs aren't the most tolerant devices.

author: mnm972
author_rank: Newbie
timestamp: May 22, 2016, 05:21:41 pm
content: Quote from: botcrusher on May 22, 2016, 05:06:44 pmThanks botcrusher,I will try to find the same but I didn't have luck till now, I don't have datasheet of the mobo, it's the best I could do.Generally if i re[place the mosfet with the same characteristics but put higher voltage, it should work?Thanks

author: botcrusher
author_rank: Regular Contributor
timestamp: May 22, 2016, 05:44:35 pm
content: if it has the same characteristics yes, you can probably get away with itbut ripple of any kind could make the cpu do wonky things, and is why they use several MOSFETs and caps in parallel.Worst case scenario, as little as +.1V can fry itThen again, I've seen aging Pentium 4 boards with venting caps just keep going (why won't you die damnit!) So YMMV.Obviously this board is a bit more sensitive since it isn't posting.Now, I'm curious as to how you were getting a error message at all considering a short on the 12V line would have the ATX supply trip. damned OEM equipment.

author: CaptainObvious
author_rank: Contributor
timestamp: May 22, 2016, 06:05:48 pm
content: Just out of curiosity, have you tried a different power supply anyways? And/or verify all the adapters are plugged in? I made a living building boxes for a hand full of years... and spent more time than I should have researching that issue on a brand new mobo oncewas getting some lights (I seem to recall a green light, but it's been a while), but no post.. turns out I missed the most commonly missed adapter! The CPU power adapter..http://www.playtool.com/pages/psuconnectors/connectors.html#atx12v4I've seen multiple PSU where only that "adapter" seems to fail, I was able to verify by keeping the failed PSU in the PC, and using another known working PSU and just used its 4-pin, and was able to function again. Of course, when you're at a client location, you just put a new PSU in and get them working and get on your way... never did spend time testing much more than that.When you work with computers every day, you seem to see a trend.. and 9/10 times a failed post call is from a bad PSU. Very rarely do I see issues with motherboards, but that's not to say it doesn't happen..

author: mnm972
author_rank: Newbie
timestamp: May 22, 2016, 06:07:01 pm
content: Quote from: botcrusher on May 22, 2016, 05:44:35 pmYes I know but this is how dell PC work,You can see it this video:

author: mnm972
author_rank: Newbie
timestamp: May 22, 2016, 06:15:49 pm
content: Quote from: CaptainObvious on May 22, 2016, 06:05:48 pmHi CaptainObvious,No I didn't try other PSU, I have checked its voltages, and it was ok,Also I have shorten its boot leads to check the PSU, green and black on the ATX adapter and it worked, only when the 4 Pin was out of the mobo.I have tested the mosfet and it has short on all its pins.The challenge now is how to remove? any technique you can suggest?Thanks