VRM Mosfet replacement with non originals

[JorgeHernan]

Hi guys
I have some NEC 2sk3296 blown but i can't get them at any stores over here.These are some old socket 370 and some 462.Can i replace them with some IRFZ44 will it work?
Thanks you

[stj]

Re: VRM Mosfet replacement with non originals

i would need to check the datasheets.

i'll say this though, you shouldnt mix fets.
if one is dead and there are a set of 3 - replace all 3.
that way you wont get any imbalance on multi-phase power circuits.

[seanc]

Re: VRM Mosfet replacement with non originals

Sometimes, the manufacturers are generous and will send free samples - thank you Niko-Sem!
Doesn't hurt to ask, all they can do is say no.

[precision001]

Re: VRM Mosfet replacement with non originals

I was wondering why do IC mosfets need 8 legs - 3 for the source and 4 for the drain? What advantage does this have? I'm thinking of experimenting with a board, and removing all but one pin for source and drain, just to see what happens.

[stj]

Re: VRM Mosfet replacement with non originals

the legs act as heatsinks and 3 legs will carry 3 x the current.

[precision001]

Re: VRM Mosfet replacement with non originals

As far as testing them goes, for a P channel would I just measure resistance S-D(pos terminal on S) ? I have come across dead boards and found some mosfets measuring as low as 50 ohms. I presume they are bad - but there doesn't always appear to be any signs of damage - they look perfectly fine.

[JorgeHernan]

Re: VRM Mosfet replacement with non originals

i would need to check the datasheets.

i'll say this though, you shouldnt mix fets.
if one is dead and there are a set of 3 - replace all 3.
that way you wont get any imbalance on multi-phase power circuits.

Yes i already know that . I learned the hard way some time ago when replaced one shorted NEC 2sk3296 (instead of replacing the 3 present on the pcchips 810 i only replaced the shorted one) with an irfz44.It worked, got video and all but only for a couple of seconds until the irfz44 started to melt and went up in smoke.I guess that happened because of the imbalance you mentioned.I wasnt able to solder the irfz44 transistor body to the board because of not having any heat gun, so that made things worst because it could not dissipate enough heat, as the the originals did.

[precision001]

Re: VRM Mosfet replacement with non originals

Could you connect a bad mosfet source to drain to force it on? I observed a (functioning) gateway laptop once that had the source of one mosfet tied to the drain of the other mosfet in the pair. I believe they were 4407s. Does anyone know why this caused the circuit to work? How could I use this information to test mosfets on a motherboard?