Author Topic: Replacement for power mosfet on PC motherboard help.  (Read 6306 times)

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Offline mnm972

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Replacement for power mosfet on PC motherboard help.
« on: May 22, 2016, 08:52:41 am »
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 GAK643
See 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 ok  http://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!
« Last Edit: May 22, 2016, 11:57:04 am by mnm972 »
 

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Offline Whales

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Re: Replacement for power mosfet on PC motherboard help.
« Reply #2 on: May 22, 2016, 11:06:35 am »
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.
 

Offline mnm972

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Re: Replacement for power mosfet on PC motherboard help.
« Reply #3 on: May 22, 2016, 12:05:09 pm »
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.

Thanks 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?
 

Offline viswesh

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Re: Replacement for power mosfet on PC motherboard help.
« Reply #4 on: May 22, 2016, 12:32:21 pm »
according to datasheet it is N-channel MOSFET, the part number itself tells 09N03L  N is for channel.. i think it is okay

thank you.
 
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Offline mnm972

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Re: Replacement for power mosfet on PC motherboard help.
« Reply #5 on: May 22, 2016, 04:39:12 pm »
according to datasheet it is N-channel MOSFET, the part number itself tells 09N03L  N is for channel.. i think it is okay

thank you.

Thanks viswesh,
You are right, I checked in the datasheets and it is N channel, I think the part is IPD09N03LA G
Package 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!
 

Offline botcrusher

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Re: Replacement for power mosfet on PC motherboard help.
« Reply #6 on: May 22, 2016, 05:06:44 pm »
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.
 

Offline mnm972

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Re: Replacement for power mosfet on PC motherboard help.
« Reply #7 on: May 22, 2016, 05:21:41 pm »
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.

Thanks 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
 

Offline botcrusher

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Re: Replacement for power mosfet on PC motherboard help.
« Reply #8 on: May 22, 2016, 05:44:35 pm »
if it has the same characteristics yes, you can probably get away with it  :-// but 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 it
Then 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.
 

Offline CaptainObvious

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Re: Replacement for power mosfet on PC motherboard help.
« Reply #9 on: May 22, 2016, 06:05:48 pm »
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 once :)  was 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#atx12v4

I'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.. :)
« Last Edit: May 22, 2016, 06:13:17 pm by CaptainObvious »
 

Offline mnm972

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Re: Replacement for power mosfet on PC motherboard help.
« Reply #10 on: May 22, 2016, 06:07:01 pm »
if it has the same characteristics yes, you can probably get away with it  :-// but 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 it
Then 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.

Yes I know but this is how dell PC work,
You can see it this video:



 

Offline mnm972

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Re: Replacement for power mosfet on PC motherboard help.
« Reply #11 on: May 22, 2016, 06:15:49 pm »
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 once :)  was 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#atx12v4

I've seen multiple PSU where only that "adapter" seems to fail, I was able to verify by keeping the "f=ailed 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.. :)

Hi 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

 


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