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.

shabaz Of course the hard drive was the first thing I tested. It works great and the partitions show fine in a Windows machine. (5 NTFS partitions I believe)

Yes XBOX is X86. It's literally just an AMD APU running Windows 10 specialized for a game console.

I just measured across the capacitor holes. (Caps are not present at the moment, tested them separately. They are fine. Around 820uF which is their marking.)

The capacitor holes from negative to positive result in:
C8E3: 1.7 ohms

C8E2: 1.7 ohms

C8E1: 0.8 ohms

C8D3: 0.8 ohms

C8D2: 0.8 ohms

C8D1: 0.8 ohms

Further testing:

R9E5: 2.4 ohms

R9E4: 2.3 ohms

R9E3: 1.2 ohms

RT9E1: 8000 ohms (8kohms)

TP9G1 GND --> TP9F1 CPUCORE: 1.7 ohms

TP9G1 GND --> TP9D2 GFXCORE: 0.8 ohms

The small chip may well be a MOSFET driver, the chances of them going bad are pretty slim.

As for your readings ... I'm not sure what that could mean - if not the MOSFETs, maybe that's actually current flowing through the actual CPU/GPU chips? I tend to avoid mindless probing across pads that aren't just across "one" component because there's always a chance of interference or current being driven into things which shouldn't be driven in such a way.

Does the resistance hold stable or does it change after a few seconds? Are there no non-obvious solder-splashes, or board getting pinched/crushed at locations (especially important for multi-layer)?

- Gough

Indeed.. resistance readings are not something that make it easy to fault-find within the circuit. Especially if there's no known working xbox to compare to.

By chance I've got a Intel x86 PCB on my desk (a working one) and although I don't see resistance values as low as those on the power rails, they are still in single-digit ohms.

But still fairly meaningless.

I mean, thanks but that doesn't help me move forward much, everyone.

What can I do to positively affect this situation?

Without understanding what's wrong, all I see is bits being pulled off at random.

This is not recommended, so better we stop that - there is a severe risk of causing more damage by powering up as you have done, with one of the rails deliberately unpowered - and if no concensus is reached on how to proceed, maybe there is no magic solution just yet.

Perhaps if you come across another xbox, then it can be compared to see where the anomalies are. Or maybe some diagnostics exist - either something that plugs on, or some LED blinking pattern.

Or maybe someone who has already come across the issue described in this thread may read it one day, and provide the answer.

It isn't random.

It might help to go through what has been said in the past.

At Gough's advice I'm going to replace all of the MOSFETs. Thing is, I'm not convinced they're bad.

I thought a good strategy might be to remove components that are likely to fail and test for grounding out again without them.

If, as you say, the X86 rails practically ground out too, maybe that's a dead end and I should look for other common issues.

Exactly, I'm not convinced it is a dead short yet - but we're still having the conversation. Maybe someone will interject and correct me since I'm only assuming that 1-2 ohms may be acceptable.

If you take the device to a repair shop, they will have that conversation but you just won't hear it. Here it's in the open.

Replacing a MOSFET is one thing, but powering up with it removed is very different. That wasn't anyone's advice, and anyway these are just suggestions - I don't know how many xbox experts are online here, so the suggestions are sometimes a bit more vague and general, unless people are 100% sure - and right now I'm not, but maybe others are.

I agree about not powering it up, and would love if we could move on from that point.

I thought a good strategy might be to remove components that are likely to fail and test for grounding out again without them.

That strategy may work, but there are risks along the way. I can't assume your experience level, and I may repeat myself at times to emphasise the importance of some points. I didn't mention how severe such a thing (that shall not be repeated) could be, so I'm afraid I chose to repeat it.

Also, you'll find some engineers ask a lot of seemingly obvious questions like "was the hard drive checked" - because they do not know you, and from experience plenty of people say things like "I checked everything" when clearly they have not. I'm not suggesting that is you - I'm suggesting that I have no way of knowing, so sometimes people ask twice, in different ways.

I thought a good strategy might be to remove components that are likely to fail and test for grounding out again without them.

That strategy may work, but there are risks along the way. I can't assume your experience level, and I may repeat myself at times to emphasise the importance of some points. I didn't mention how severe such a thing (that shall not be repeated) could be, so I'm afraid I chose to repeat it.

Also, you'll find some engineers ask a lot of seemingly obvious questions like "was the hard drive checked" - because they do not know you, and from experience plenty of people say things like "I checked everything" when clearly they have not. I'm not suggesting that is you - I'm suggesting that I have no way of knowing, so sometimes people ask twice, in different ways.

My experience level with electronics is pretty basic but I did take the time to research common XBOX problems before I started removing parts. Yes.

Gough Lui shabaz

Hi friends! You have been quite helpful. Thanks very much!

I think I am ready to go buy some parts and see if I can make any difference with this thing. I'm having fun here so I want to keep trying to fix this thing.

My next steps:

1. Order some replacement parts
2. Replace all of the parts in the power rails at once
3. Try with power on again with all parts present

Those are the parts I know of. To figure out what a surface mount capacitor is if it's unmarked, would it make sense to remove a few of them and average the capacitance value of them? Are they polarized if they are not marked? (I can make note of how they're connected to ensure I test the right polarity with them removed from the board.)

I figure if I'm going to bother with the MOSFETs, I may as well buy a bunch of surface mount capacitors and resistors too to play with. I can then replace those too and make sure everything is within spec.

Again, I understand spec is hard to understand without a known good XBOX One S motherboard to compare to.

Do you have any advice for this stage?

Thanks

- Lil

Unfortunately I only have general info, I don't know what others would do, but I would assume all resistors are working, unless I knew the board may have been bent, or if there was discoloration - I've never seen a resistor fail otherwise. But if you wish to replace or test it first, out-of-circuit measurement should match to within a few percent of the marking on it (some tiny resistors will have no marking). The last digit is usually the number of zeros to add to the previous digits.

For surface-mount capacitors, those are ceramic types, and they don't fail in operation either, although they can definitely fail if cracked, e.g. heated from one end or flexed. I believe that is far more likely with tiny capacitors, i.e. millimeter-sized, which these ones are not in the photo (at least, I've only succeeded in damaging the tiniest capacitors in that way - but I could be making an incorrect assumption) or those in vibrating/flexing environments. The largest ones in the photo may be anything from 1uF to 10uF or something, but it's a huge guess, and any IC datasheet for the DC-DC converter circuit should be checked. Probably the voltage rating for them is 6.3-10V, but there is no way to be 100% sure. The smaller capacitors I have no idea, it would be too much guesswork, they could be 100nF or 10nF or anything else, and it needs the IC datasheet to be consulted, or a known working one to be measured. Sometimes that is luck, since the entire part number won't be marked on the IC - so google may help on that, or if anyone has a components list in that area. Also, those capacitors are likely of type 'X7R'. Often the larger ones are not cheap. If you think one is faulty, then the capacitance of a known working one could be measured out-of-circuit (since the three DC-DC converter circuits look identical - they are just set at different voltages). The capacitors are likely identical value, to reduce BoM costs. The values of the capacitors could vary by say 20% and still be fine - they have this variation from new, it won't be a fault causing this.

From what I can tell, I might have jumped the gun guessing a power issue. It might have been doing a boot loop due to the APU needing to be reflowed. I tried to do that, but I didn't give it much heat and it may have failed to reflow the solder. It may be the APU actually dead, but that's pretty rare.

It seems to be a VERY common problem with the XBOX One S that the system will get into this state of "start up sound" then "shut down sound".

Others on the Internet seem to think it's APU related.

Have you given up on this project? I get these in all the time and while quite often they are fixable, sometimes they aren't. Just wondering if you ever figured out the problem for sure. Let me know if you get a chance.

Thanks!

Steve

I don't know what the APU is, but if it is a physically big chip, it will be extremely difficult to reflow without specialist tools and procedures. You can check out 'Louis Rossman' videos on YouTube to see if he shows how to do large chips.. it's a specialist thing.

I did see for PlayStation repairs, full-blown ovens are used for similar repairs, to get the heat energy to the whole of the large chips (aluminium reflective covered baffles protect the rest of the PCB). Another option could involve a pre-heater.

With no experience myself on anything larger than 1cm2, so take this opinion with a pinch of salt, I think chances are near-zero with a large chip and just a low-cost handheld hot air tool. Even at 1cm2 I use a pre-heater, since my handheld hot air tool is only a few hundred watts.

I just got one of these... did you manage to change the ic ?

Hi Javed,

What IC are you referring to? If you're referring to the APU (large chip), there's no hope without specialist equipment, to remove and replace that.

We're talking the cost of multiple Xbox units. You'd ideally need a specialist oven costing $1000 or more.. (and a lot of experience using it).

I am talking about the controller chip highlighted there i think its the pic you sent couple of posts able. I do not have any voltage when i put red probe on gate and black on resistor.

black on gate registers .680ish so i am leaning towards the controller being bad?

Hi there ijaved!

I forgot about this project. I still have the board sitting in a cabinet in my work room.

The component you are pointing to in the image is a MOSFET. It is quite possible it has failed. They are very delicate inside despite the fact that they work on huge currents.

I think I destroyed my XBOXONES so I am not sure if I can be much help. I also made use of the HD and PSU for other projects. (I used the PSU to power a video card on one of those M.2 to PCIe16x adapters.

shabaz  is really smart and so is Gough Lui

Read what they wrote above in response to my comments and it might help you.

Hope this helps!

  - Lil