funny they 2RROD'd when inside the chassis and also when completely stripped, and only booted if there was pressure on the RAM chips.
When you press the board anywhere you change the form of the board and for example causes the GPU chip die to touch the heatsink better.
Or for example on some cases the thermal element of the GPU (GPU has two) for either the GPU core or EDRAM has it's ball cracked and the heat signal is not reaching the HANA/ANA chip, making the SouthBridge have an wrong reading in return.
when the RAM chips were reflowed the consoles booted again, and have done so to this day (friends consoles that only i mod/fix)
That's not scientific as to "reflow" you have to dismantle the heatsink assembly and the act of dismantling and reassembling more than often cures overheat issues.
I acknowledge the fact that removing the mobo is enough to cause RROD, but this was not the case for these two particular boxes.
Again, that is not scientific as there's too many variables for you to get misleaded by ...
the RAM chips were defo badly soldered to the board, and had to be reflowed to work correctly.
Poor/faulty contact in the RAM data or address lines will give you 0102 (E18)
Short circuit in the RAM data or address lines will give you 0110 (E24)
While these faults MIGHT happen under the RAM chips, their area, size and the fact that they do not heat enough to cause damage to their own solder makes it extremely unlikely for them to be the cause of the problem.
I suppose I know what I am talking about ...
13GUPs, 3 CPUs all screwed up, taken out from boards that had them replaced with good chips
The CPUs in particular were replaced to revive boards which were ruined by lost DVD KEY and had updated bootloaders. The donors were either JTAG'd or JTAG'able so it was obviously worth the effort.