You cannot belive what happened and I do not understand it at all either… I could find 2 caps under the cpu on the back of the board connected to the 3,3V rail. I removed those caps and now I have a full short to ground on the 3,3V. How the hell can this be??? I did not mess up anything there.
Hmm this is possibly a good thing, whats the resistance?
5 Ohm. Shall I try now the IPA trick. Basically there is nothing to loose 
Maybe we are going somewhere?
Yeah why not, just limit the current just in case the short spontaneously clears or opens up, which wouldn’t be good. maybe start at 100mA then pick it up from there.
It should be capable of drawing about 600mA at the very least which is more than enough to expose a bad capacitor somehwere, just make sure your using some heavy guage leads from your PSU connected up to some small length fly leads on the board.
Btw on one of my donors there is at least one pad on SoC connected to this rail… i hope it’s not the SoC at fault here. Lets hope it was a side issue on my donor
btw the name of the other short finder was the tone ohm if i’m remembering right, there is a few which go by different names.
I vaguely remember seeing the schematic for one of these commerical products…
And now my 170Ohm short is back 
I connected my PSU and was wondering why it is only taking 100mA. Than I measured again and it is now 170Ohm.
Cannot be that the CPU was still hot after desoldering teh caps and this fooled me?
quite possibly, the thermal expansion wiill skew readings… maybe this board suffered impact damage at some point and a ball is floating around under the SoC… would explain the wierd reading of 170ohms (contact resistance)
Or worse maybe the SoC is internally damaged… but we’ll pretend not for the time being 
Please just let me know if I annoy you I do not want to waste your time anymore. You helped me already a lot and I really appreciate it. How could I thank this to you?
No not at all man! this is interesting, as i said earlier, faults such as these cause me to have to look into a few things which ultimately helps me later on down the line when diagnosing my own faults
What if I try to reflow the SOC? I can see the biggest changes in resistance if I heat up this area. As you also told could be that than the board is expanding and the solder ball is touching the pad.
If the root cause of the fault is a stray solder ball below the SoC, then it’s likely this ball will bridge to the ground plane entirely, and i expect your 170ohm reading will read close to zero
I suppose it wouldn’t hurt to try it to begin with, preheat the opposing corresponding side of the board at about 200C for a few minutes then flip the board over and add a bead of flux around the SoC, continue heating the opposing side of the board for another minute to allow the flux to be drawn in below the SoC and then flip the board once again, set you hot air to about 400/420C at low to medium airflow, monitor the SoC shield frame to give you a clue as to when your up to reflow temps.
Afterwards allow the board to cool, and clean everything up while it’s still warm, check the readings again on this rail, if the value has changed, either for the positive or for the worse then that settles it i think and points to the SoC.
If that’s the case then you can repeat the above, only this time remove the SoC entirely, if it was indeed the cause of the fault the reading on the shorted rail will clear.
The reason for heating the underside of the board to begin with is so not to expose the SoC to excess heat, it doesn’t take much to kill the SoC when applying too much heat, the epoxy bonding material will discolour and the low voltage critical rails (which can be checked on the SoC caps) will short out.
Soc shield temp should be around 260C?
SoC shield should be removed entirely prior and thermal paste cleaned up.
after the preheat on the reverse side of the board and adding the flux… during the reflow stage your looking at the SoC shield frame, once the lead free solder is molten then it indicates the SoC is up to reflow temps
Hope that makes sense
Btw in order to remove the SoC shield cleanly, if you haven’t done this before, insert a scalpel/X-acto blade between the tabs and twist outwards, the tabs shouldn’t be grabbing, go round all and pop the shield off. careful not to scratch up the board while doing this
Don’t use a dental pick or other 
Also, i fogot to mention, shield the EMMC connector and possibly the speaker connector prior to this, they will be the first to burn during the reflow, i typically use those metal PCI knockouts on cheap desktop PC’s and bend them in such a way in order to shield them and prevent this.
I have done it a few times already. 2 or 3 times. Yes I covered all the connectors and they all survived and as expected my full short is back so most probably this is the issue…
and has it remained a ful short consisistently? take it its close to zero now?
It is still a 3,4Ohm short but the board is still around 80-100C I assume…
once it’s cool, we shall see
I think this is the end of the story because I will definetly not be able to reball the APU 
Now it is in the IPA bath lets power it up with the PSU