Xbox One Blown Mosfet

[mmartell]

Re: Xbox One Blown Mosfet

So I should be looking for a fault common to the 12v and low voltage rails... unless of course the faults are unrelated but that's probably less likely.

Will have another look soon.

[momaka]

Re: Xbox One Blown Mosfet

if the cpu or other large bga chips have ceramic caps on top, meter across the caps for a short.

That wouldn't help either for two reasons:

1) The caps on top of the large BGA chips are typically across the BGA chip's Vcc/Vdd, or other low voltage supply lines for the chip. Almost guaranteed that there's not a single pin on any of those large BGA chips that connects to the 12V rail directly. So that means, even if one of those caps were shorted, that wouldn't explain the short-circuit on the 12V rail of the Xbox.

2) high-power chips tend to have very low resistance (no uncommon to see 10 Ohms or less). So when you measure those ceramic caps on the BGA chips, you will most certainly get a very low resistance and think they are shorted when they aren't. This is one mistake I see very often when rookies troubleshooting motherboards. So don't fall for that one!

[stj]

Re: Xbox One Blown Mosfet

that wouldnt explain your short.
if the cpu or other large bga chips have ceramic caps on top, meter across the caps for a short.

[mmartell]

Re: Xbox One Blown Mosfet

I haven't tested any of the removed parts I just checked continuously for a short condition at the port, which remains. Seems a somewhat common fault on these for the southbridge to fail by cracked solder joints causing the symptom of "turns on then off". I wonder if repeated attempts at powering up somehow overdrive the phase circuit blowing up mosfets eventually.

[momaka]

Re: Xbox One Blown Mosfet

I took off a shit ton of parts including all the components in the phase circuit of the blown mosfet and the main controller and still registers short.

Interesting.
So none of the "upper" MOSFETs between 12V rail and chip outputs were blown? Perhaps a ceramic cap between 12V and ground is blown then? Or some controller IC that is powered from the 12V rail.

Where is the board-specific info housed anyway or is that a quick dead-end ?

I would save that as I last resort. Who knows what else is written on that chip that may be specific to the board it's in now. And if it's coupled to the CPU/GPU with a special code, forget it, because then you will also need to move that to the new Xbox board. Of course, I am just saying *IF*.
I'll be upfront that I know nothing about the Xbox One. I've worked on a ton of Xbox 360s, but not a One. That said, I imagine many parts of the design would be re-used, as I've seen that with many other board manufacturers.

[mmartell]

Re: Xbox One Blown Mosfet

I took off a shit ton of parts including all the components in the phase circuit of the blown mosfet and the main controller and still registers short. Nothing to lose now but to remove more parts. I know this isn't the proper way to do this but truth is I was hoping to get lucky as I have a complete parts board which doesn't appear to have suffered the same affliction.

Where is the board-specific info housed anyway or is that a quick dead-end ?

[momaka]

Re: Xbox One Blown Mosfet

I saw one last week on eBay with a "no power" problem. Could have been the same issue, so who knows.
I'll take bad MOSFETs any day over doing GPU/RAM like on the Xbox 360 - those things had way too many problems. At least they were easy to take apart, and test as is "barebones". PS3 was the worst, IMO.

[mmartell]

Re: Xbox One Blown Mosfet

For the xbox one ? No idea, I have only seen it mentioned on the greater Web in the youtube video linked to by vince.

By the way in that video the guy mentions a resistor is missing from the board and mine is missing as well in the same location. Odd.

[stj]

Re: Xbox One Blown Mosfet

is this a common problem btw?

[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.

[mmartell]

Re: Xbox One Blown Mosfet

My shorts are source-drain if I recall.

[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

Good ideas. Hope to get down to this soon.

[stj]

Re: Xbox One Blown Mosfet

maybe an esr meter could trace the short.

[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

[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.

[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

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.

[mmartell]

Re: Xbox One Blown Mosfet

Thanks vince will have a look at that soon.

[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