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Replacing MOSFET

V

Vjiper

Junior Member
I removed a cracked MOSFET from my dead Slot 1 mobo. I desoldered what I could and pried the rest off with a butter knife.

I found out as much as I could about the MOSFET. It is a STB3015L N-CHANNEL 30V - 0.013 OHM - 40A D2PAK/TO-220 STRIPFET POWER MOSFET. I have searched Digi-key and found some similar MOSFETs. The closest I have found are 38A or 54A. Would either of these be a suitable replacement?

Any help would be appreciated since I know very little about MOSFETs. I don't even know how I am going to get a good one back on the motherboard.
 
You could try one of the replacements and see what happens.

SMPSs are quite fickle, and could quite easily stop working with a minor change - Is that mosfet part of the CPU voltage regulator? If so, you could toast the CPU if the supply fails.

Also, if you had to pry the remains of the mosfet off the board, did you delaminate the board? This would be terminal for the high-current circuits.

As a quick check, just make sure that the replacement has at least the same current rating, and frequency handling. Also check that gate sensitivity is similar (i.e. if the original is logic-level gate drive, make sure that the replacement is otherwise it won't work).

I suppose, if you're willing to risk the board and CPU it would be worth a shot.
 
The MOSFET looks to be part of the cpu voltage regulating. I am not too concerned about frying the chip or the board since the board doesn't work to begin with which is why am am replacing the MOSFET and the CPU is a P2 350.

I don't think I delaminated the board. I just pulled up some of the thin metal that was underneath the MOSFET. I don't think this will be a problem.

I'll check on MOSFET a bit closer but I don't think I should have any problems.

Besides, I have nothing to lose except for a few bucks. Trying to fix something that isn't important is what I consider fun.

I'm not sure what MOSFET stands for but it is metal-oxide something.
 
Thanks for the help. I also have to pick up some new capacitors.

From what I have found on various web pages, I have decided to get a MOSFET with a higher current rating and some better capacitors.

Thanks for telling me about Mouser. I wasn't too keen on paying sales tax.

If any one has a nice guide about soldering parts on a mobo it would be appreciated. Just to get me headed in the right direction before I break something.
 
When soldering the MOSFET, make sure you have a "heat sink" attached to the lead you are soldering. Otherwise the heat from the soldering iron will go into the microchip and fry it.

63/37 Tin would probably be the best to use for solder, since it melts at the lowest temperture compared to any other ratio.
 
I have some Rosin Core solder that is 40% tin, 60% lead that I think will work. I hadn't thought of frying the chip. I'll have to devise some way of keeping it cool enough but I think I have the general idea of how to do it. I just have to keep the chip attached to a dense metal like a heatsink from a socket 7. The soldering iron I have isn't grounded to the outlet but I should be able to run a wire from it to the concrete floor.

Is the drain on the MOSFET for cooling or does it carry an electrical current?
 
Sorry forgot to finish off the "heat sink" on the lead being soldered. What I have seen and used was needle nose pliers with a rubber band on the grips to give it pressure to remain closed. Something similiar to that is a tool that can be purchased.
 
hehe, that's funny. I never expected one acronym to come back with two different meanings.

I hate waiting for packages to come in the mail. I want them teleported right to my doorstep.
 
I replaced the mosfet and the capacitors. It still doesn't work. I'll try some other things when I get more time but right now I just don't have time.
 
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