4 
1 PSU 11.94V, White Light, Start Beep, Then Turn Off Beep
Update: I have advice from the element14 forums to replace all of the MOSFETs at once. I have yet to try this. I have some light experience using the hot air rework station and Gough Lui gave me some very good advice on how to improve my technique.
Does anyone else have some advice in this regard?
First disassembly and diagnosis:
Tried to swap the MOSFETs:
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I have an XBOX ONE S that I bought as “for parts” on eBay and the owner says it was kept in a clean house, etc. It is indeed clean inside. No signs of water damage.
The PSU is also fine. The APU had a TON of thermal grease all over the surface mount capacitors. I didn’t remove that yet but I did re-apply some arctic silver and I used a more reasonable amount.
The symptom I see:
Console when plugged in does a few quick pulses to the APU fan. Is it trying to init?
Console when eject is pressed makes the eject sound, then the shutdown sound immediately after.
Console when power is pressed makes startup beep and then shutdown beep immediately after.
I don’t know what kind of issue I’m getting yet. Is there a JTAG interface or some way to do further diagnosis on this thing?
11.94V sounds perfectly fine for a 12V rail. Should I simpy try plugging a PC power supply into the motherboard to see if it will boot?
Any links or info on diagnosis would be appreciated.
Thanks in advance!
[edit]
Photos of my motherboard:
I need to find a place to buy a handful of both of these MOSFETs.
4C50 and 4C55N
Ist dies eine gute Frage?
1 
5 Kommentare
Aha! In the image you can see the CPU filter capacitor is registering just 1 ohm! The others are pretty low too but I bet if I remove that one it’ll at least boot. I have a server motherboard with a broken socket that I can steal capacitors from. Might replace the whole row if necessary.
von Lilithe Lotor
Looks like I was wrong. That capacitor I removed still offers up almost exactly the uf value on the tin. So that was another dead end. Hmm... One weird thing, all of the test points register 60Hz but not 110V. So thankfully the PSU isn't pushing wall socket voltage through. But that frequency is weird. My multimeter needs a charge though so I'll measure that again after it has.
The entire power area for the APU offers almost no resistance to the ground plane which is worrying. Again, need to charge that multimeter and re-check.
von Lilithe Lotor
Power on with no heatsink, the processor doesn't even warm to the touch. CPU, GPU, and other test points around the board pulse to 1-2V and then turn off fast.
Can't help but think it's related to the very low impedance between ground and positive on the V rails for the CPU/GPU. Is that normal?
USB port is charging the multimeter :)
So that 5V rail from the southbridge is working.
Lots of 12V test points are consistently 12V (11.94V)
von Lilithe Lotor
https://youtu.be/4XZNdUTsuTc
von Lilithe Lotor
Your bot is broken, iFixit. My last comment above this one was not spam. It was a further explanation of a technical issue that might help someone else in the community.
von Lilithe Lotor