Xbox One Blown Mosfet

[mmartell]

The 12v line is shorted right at the power connector. Nothing looked bad until I removed the heatsink and found a destroyed mosfet. After removal the short remains.

This component is in a bank of five identical circuits as shown in the pic. I'm getting strange reading off these, some read shorted whIle others don't. Not saying it's not possible but something tells me not to trust these readings just yet.

As this board is a challenge to work with because of its thermal mass was hoping for a little guidance. Searched for schematics but evidently there are none.

What's the best course of action ?

[vinceroger69]

Re: Xbox One Blown Mosfet

Maybe send this man a message via his you tube account as he may of saw this isssue before and maybe willing too advise
https://www.youtube.com/channel/UCtf...eEY_vq_UOL4PDQ

[stj]

Re: Xbox One Blown Mosfet

if it's a 5phase psu,
get the part number from the controller i.c. and there may be a schematic in the datasheet.

[budm]

Re: Xbox One Blown Mosfet

Can we get good clear straight shot pictures of the board top and bottom and then the closed up of that section?
Those 5 switching circuits look to be BUCK Converter, so I would check the Diode for the output section and the filter caps too.
http://www.learnabout-electronics.org/PSU/psu31.php

[mmartell]

Re: Xbox One Blown Mosfet

Sure thing, bud, will get them as soon as I can.

[mmartell]

Re: Xbox One Blown Mosfet

Here you go, hopefully they are ok.

[stj]

Re: Xbox One Blown Mosfet

so what's the part number on that ON-semiconductor controller chip on the right in the first foto?

[mmartell]

Re: Xbox One Blown Mosfet

NCP4204. I could only find the data sheet for the 4200 for which all four buck converters were wired identical save for a feedback circuit on one of them.

[mmartell]

Re: Xbox One Blown Mosfet

NCP4204GAC1328G, for completeness

[vinceroger69]

Re: Xbox One Blown Mosfet

The 12v line is shorted right at the power connector. Nothing looked bad until I removed the heatsink and found a destroyed mosfet. After removal the short remains.

This component is in a bank of five identical circuits as shown in the pic. I'm getting strange reading off these, some read shorted whIle others don't. Not saying it's not possible but something tells me not to trust these readings just yet.

As this board is a challenge to work with because of its thermal mass was hoping for a little guidance. Searched for schematics but evidently there are none.

What's the best course of action ?

https://www.youtube.com/watch?v=nlFwuloe3lI

[mmartell]

Re: Xbox One Blown Mosfet

Thanks vince will have a look at that soon.

[mmartell]

Re: Xbox One Blown Mosfet

Yes that was the exact same mosfet that blew up !

But after removal he had a gate to source short where I have a drain to source short on four of five mosfets which I'm guessing shouldn't be there ?? The 5v Standby pin on the power connector is still shorted to ground as well.

I think I will start removing parts as a way of locating the short.

[vinceroger69]

Re: Xbox One Blown Mosfet

he does good videos maybe send him a email through his youtube channel see if hes had this fault before may save you some time fault finding but i also guess it helps if like him you have a spare board on hand too keep swopping parts with saves having to wait for orders etc.

[mmartell]

Re: Xbox One Blown Mosfet

I've got a broken parts board on the way. First thing is to remove the short - soon as I get some time.

[mikkhh]

Re: Xbox One Blown Mosfet

remove all those 1007r3 inductors that are connected in parralel (the all 5 should be, but if you can then you should remove all those five inductors)to the shorted one. If the short is still in there then you have a fried cpu/gpu chip. That´s it. By removing inductors you can tell where the short is - in the vrm side or the gpu/cpu side. And when you are going to replace the parts replace the mosfets in a set (lower and upper) + the phase driver IC

[stj]

Re: Xbox One Blown Mosfet

maybe an esr meter could trace the short.

[mmartell]

Re: Xbox One Blown Mosfet

Good ideas. Hope to get down to this soon.

[momaka]

Re: Xbox One Blown Mosfet

maybe an esr meter could trace the short.

Not a chance.
Those board traces are way too thick.

Just have to get it open and start testing. Since the 12V line appears shorted at the power connector, I would check all of the high-side MOSFETs on the CPU/GPU VRM first. Any MOSFET that shows short-circuit between Gate and Source or Gate and Drain is a very probable suspect and should be removed and tested outside of the board again.

[mmartell]

Re: Xbox One Blown Mosfet

My shorts are source-drain if I recall.

[momaka]

Re: Xbox One Blown Mosfet

My shorts are source-drain if I recall.

That's normal for *some* of the MOSFETs (since the CPU/GPU has a very low resistance and will make MOSFETs on the lower side of a buck converter to appear as shorted).

So do check if there are some that have Gate to Source or Gate to Drain short-circuit... or resistance less than 100 Ohms.

If not, then I guess it's time to start pulling MOSFETs and testing them one by one outside of the board.