Haha I was thinking why did you close the topic
https://www.theguardian.com/technology/ ... ngineeringMaybe it was a whisker. This is effect when a tin needles build up along the electric field. PEX_RESET is +3.3V so it maybe was a 6 ohm whisker to the ground.
6 ohms is rather a strange value. This is normally open circuit when the semiconductors are fried in I/O pins, at least all pis I have found damaged look like open or almost open.
There is another way to burn such a whisker by a strong current. This PEX_RST pin is 3.3V capable so you could connect 1-3V directly from the power supply and it should not do anything wrong. Logic level is to weak to do it but by a direct PSU voltage should burn it as a fuse.
It is risky because if there is something stronger like a liquid metal you would burn PCB.
So the first should be IPA + compressed air and then maybe 1Volt from the power supply. 1V from the PSU definitely would burn such whisker and should not fry the PCB. Soldering on a proper reflow machine is the safest and at once will repair all other joints.
I set a profile and when it reaches the reflow phase above 200'C I wait to cross 220..225..230.. and I start touching the chip. When I feel the chip is floating I stop the process and let it to cool. I press te "red" button on the Chinese reflow machine, nothing special IR6500 but it is enough plus flux 218 noname clear, transparent. I put flux around the chip, a lot of flux, then 10 minutes preheating from the bottom only to remove moisture and so on some minutes at 110'C to be sure that no popcorning will happen...
