I found them! I will order them in a week or two. Found both on Mouser and only one of them on Digikey. Digikey had both but one was only in whole reel form. I do not need $2k or $4k worth of MOSFETs.

Gough Lui Can you take a look at what I did?  https://www.youtube.com/watch?v=4XZNdUTsuTc

I made a real mess but I think this is recoverable. Maybe once I get a few known good MOSFETs it'll work?

Sorry - I've been quite busy and am at work ... supposing you didn't lift any traces or warp the board significantly, you might well be fine. However, that's not to say that the VRM didn't fail for other reasons (e.g. overloading due to a faulty CPU or shorted semiconductor is also possible).

That being said, I only had the time to jump around your video - for such boards it pays to:

- Be Patient - the board is designed with many vias to take heat away from the MOSFETs and use the copper planes as heatsinks. Hence if using hot air from the top, it can take a while to get things melted.

- Use Additional Heat - if you have access to a hotplate of sorts, it could pay to rest the board on top of it so that it gets heated from the other side as well. This reduces the possibility of warpage of the board (which can stress the traces and other BGA joints) as well as reduce the thermal energy required to melt the solder.

- Use Flux - mainly to conduct the heat slightly better and keep oxidation at bay - just remember to clean it off properly.

- Don't Scratch - scrubbing with the tweezers is asking for trouble - applying pressure before it's ready risks lifting pads, scratches components and potentially also scratches adjacent traces on a slip of the tip.

Resoldering the new MOSFETs will take some very careful work - the problem is the amount of solder required. On manufacturing lines, solder paste is pushed through stencils to leave a very precise amount which allows for the rear heat-sinking contact and all electrical contacts to make good contact. When applying by hand, it's very hard to achieve consistency - and if just pre-tinning the pads and reflowing, you will need flux and hope that you didn't supply too much/too little solder or too little heat resulting in a solder void on the thermal conduction pad (as the MOSFET could then cook and overheat).

- Gough

You are so wonderful and I can't thank you enough.

I will work patiently from now on and I have learned a lot from this process. It is actually the first time I have ever used my hot air rework station for its intended purpose. Before this I only used it to "reball" a MacBook Pro my friend owned. I got it working, amazingly!

My plan is to buy about 5 of each of the 2 kinds of MOSFET and try replacing those, as well as maybe 10 of those capacitors. That way I have plenty of parts.

My strategy will be to replace one MOSFET, test continuity to ground. If still low, replace another. Keep going until the issue goes away.

I will probably not post again until the end of the month as I promised my partner I would not buy more parts from eBay for the rest of the month. (I think buying parts at all counts so I will be on hiatus.)

Thanks again! I appreciate your guidance SO MUCH!

Another thing I forgot to mention - MOSFETs are very sensitive to over-voltage stress, and an extension of this is that they are very susceptible to ESD damage. Do avoid handling the chips with bare hands too much and work in an ESD protected environment as much as possible.

If you want to do things in parts, that's okay - but given the relatively low cost of the MOSFET and the potential that a shorted MOSFET could cause out-of-spec output every time you try to boot the unit, my philosophy is to "rework on a roll". Once you establish a pattern, it's much quicker to just do the whole lot (good or bad) in one sitting with the board still heated etc. This avoids thermal cycling which stresses the board, wasted time from downing tools and starting up again, and potentially more oxidation of solder from sitting at high temperatures after the initial good solder joint has been formed.

Also remember to clear the pads well - you may well be working with leaded solder whereas the board would have been manufactured lead-free. Mixing the two often results in matte-looking, sometimes brittle joints.

Good luck!

- Gough

Gough Lui  I tried removing the bigger MOSFETs and they seem fine, also removed the capacitors. Still a short to ground.

I wonder if it's the reeeeeeeally tiny IC in that power rail?

See video: you can skip to the end for testing.

https://youtu.be/GzWI6J4IZn4

The more I think about it, the more I think that TIIIIINY IC with a resistor on it is the first stage of the gate controlling the on/off state of that power rail.

Look at that original XBOX One image (big image with standby voltages).

That tiny IC is connected to a smaller trace that comes from that big black thing at the bottom of section 9E of the motherboard. I bet that's the control turning it on/off.

I bet those MOSFETs were fine, but I'll still replace them. I may remove U9E2, U9E1, U9D2, and then test continuity to ground again on the voltage rails.

I keep trying to remove parts to sort out where the short is.

Hi,

Across precisely what points was 1 ohm measured? Were the probes across the through-hole pads of the capacitor? Or were the probes placed elsewhere? I'm wondering if you're just measuring across the same plane inadvertently (e.g. the ground plane or some different rail) - but it's a guess, because I don't know where the probes were positioned. To a multimeter, there is no difference between a zero-ohm measurement across the same power plane, and a measurement of 1 ohm. The margin of error is large with such a measurement, when the resistance is really low.

Had the MOSFETs been in a faulty shorted condition, then that could be confirmed by testing them removed, but you've done that and the short is still present. Whatever tiny IC you're referring to, could not have been gating the MOSFETs to a shorted state, because you tested for resistance with the power off. They could not be gating the MOSFETs with no voltage applied.

Also, I couldn't tell from the video (the first one) but it seems that power was applied with one of the MOSFETs unsoldered. That's not good, because if they are all different power rails, then it could damage things if one of the rails is deliberately left unpowered while the others come up. Hopefully the system quickly powers off to try to protect from that, but to deliberately power it up with that removed is still a big risk, for no benefit. There will be no power supply rail redundancy or anything like that in the xbox - it's a consumer item, they don't do that because it saves a cost in the tens of dollars, off the end price to the customer. (And even the expensive industrial equipment wouldn't implement such redundancy at the point-of-load as far as I'm aware - I could be wrong).

That's a good call. Anyway, it measures short (yes 0.6-1.2 ohms all over the power rails).

That's why I'm thinking the tiny IC is involved because even if I removed all of the MOSFETs and the capacitors it still registers a short all over the power rails except for anywhere it previously registered 12V. Those are OL (over limit).

https://www.youtube.com/watch?v=GzWI6J4IZn4

At the end of this video you can see me testing all over the board. In 5 minutes I'll post a screenshot with indications where it is short.

shabaz

The red dots represent a short. When I ground, I ground the black probe to the rings, or to one of the test points on the motherboard marked ground.

Testing the MOSFETs themselves free from the board, they register in the megaohms of resistance. I think they were fine. I could test all of them to be sure.

[edit] TO clarify... both when the MOSFETs were installed and now when they are no longer there, it still registers a short. (0.6-1.2 ohms, very low resistance)