Xbox One S - short on ram

[damanloox]

Hi,

I've an Xbox One S that turns on for a split second and powers off almost instantly. I have short to ground on all caps near ram chips (and it's a dead short. I know in "working" machine it's low resistance but on this one it's a short). I measured mosfets and they all seem to be OK, also measured 12V - no short there. I tried to inject voltage and the board takes about 1.5 amps at 1.8V but nothing seems to heat up (ie. ram chips slowly warm up but it's minimal and they all warm up exactly the same). I don't see any hotspots anywhere (note - I don't have a thermal camera, using IPA to see if it evaporates anywhere so my "diagnosis" may not be accurate).
I inspected the board and there's no signs of liquid damage or any missing components etc.
Went through several "tutorials" but they all seem to have faulty mosfets so not my case (I think)...
Any ideas...?

[james_s]

1.5A at 1.8V is almost 3 watts, that energy must be going somewhere. It's possible the RAM is on the same rail as something else that is heatsinked though. My first thought was shorted decoupling capacitor, but I would expect that to hold the voltage at pretty close to zero.

[damanloox]

yeah I know that energy must go somewhere... It's just that I don't see it (with my rather poor equipment). I'll try again and focus on the caps (worst case scenario I'll desolder them all...
I was thinking that perhaps it's the apu - just wondering how much amps it needs to get warm to the point it starts evaporating the IPA.
Also - (best case scenario/assumption) if one of the caps is bad - would that short _all_ other caps/ram (ie. are they all on the same rail)?

[james_s]

Yes it will short anything that is on the same rail, although by passing as much current as you are, you should be able to see a pretty significant voltage drop as you get closer to the short so you might try that technique. Poke around with power connected and try to find the point where the voltage is lowest.