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Topic: Silly mosfet question (Read 362 times) previous topic - next topic

rkrishnan2012

Nov 15, 2012, 10:04 pm Last Edit: Nov 15, 2012, 10:20 pm by rkrishnan2012 Reason: 1
Hi,

This might be dumb but I have this old laptop motherboard (not so old, its a core 2 duo) and I see that this mosfet might be dead. Is there any way I can get one of these from a radioshack?

http://pdf1.alldatasheet.com/datasheet-pdf/view/180243/IRF/IRFR3709ZCPBF.html

Also, im not entirely sure it is dead because I tested it by connecting the positive of multimeter to the sink and the negative to the gate. Then I connected neg. to drain and back to sink and the diode test didn't show anything. However, on the other mosfets on the board it gave a reading on the multimeter. Am I doing the test wrong or is the mosfet really dead?

Also, if there is not the specific mosfet in radioshack, can i replace it with a similar one?
I have this one readily available here and it has the same voltage...can I use this? http://www.alldatasheet.com/datasheet-pdf/pdf/53126/FAIRCHILD/ISL9N7030BLP3.html

Thanks!

majenko

It looks an almost reasonable replacement.  The Rds_on is slightly higher, so it may get hotter and drop slightly more voltage than the existing one, but other than that it looks (at first glance - correct me if I'm wrong) ok.

Testing components in-situ is never an easy task.  You need a schematic, and you need to understand how the other components around it interact with it.
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fungus


Hi,

This might be dumb but I have this old laptop motherboard (not so old, its a core 2 duo) and I see that this mosfet might be dead.


The only truly dumb question is the question that isn't asked.

How do you know it's that mosfet causing the problem?


Also, im not entirely sure it is dead because I tested it by connecting the positive of multimeter to the sink and the negative to the gate. Then I connected neg. to drain and back to sink and the diode test didn't show anything. However, on the other mosfets on the board it gave a reading on the multimeter. Am I doing the test wrong or is the mosfet really dead?


It doesn't mean much without knowing what else is connected to it. The only way to be sure is to remove it from the PCB and test it alone.

No, I don't answer questions sent in private messages (but I do accept thank-you notes...)

rkrishnan2012

Awesome thanks guys, is this how I would test it if I take it out of the board? Also, I killed the board by accedentally plugging in the keyboard connector wrong and somehow it shorted and refused to turn on again. Any idea on other components I could try?

Thanks!

fungus


Awesome thanks guys, is this how I would test it if I take it out of the board? Also, I killed the board by accedentally plugging in the keyboard connector wrong and somehow it shorted and refused to turn on again. Any idea on other components I could try?


Almost anything on the board could be blown. This isn't a General Electronics question, you need to ask somebody who knows about laptop motherboards and the sort of things that happen if you connect keyboards wrong. If you've zapped any major component (which is likely if it won't power on) then it's probably unfixable (economically).

No, I don't answer questions sent in private messages (but I do accept thank-you notes...)

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