For $29/mo, we provide access to advanced level technicians who will answer your questions on any Macbook board related matter to the best of their knowledge promptly & walk you through how to solve your problem so you can deliver a working board to your customer.
no liquid damage signs anywhere, not dropped. at first all rails were present, cpu becoming warm but no spin. after a bit it went worse. 5vs5 and 3.3sv5 present, but PM_SLP_S5_L so no 5vs4. no corrosion sign anywhere.
Don't get any pulse at PM_SLP_S5/4_L?
PM_SLP_SUS_L present?
Are you using original Apple charger, 60/85W?
Check SMC_ADAPTER_EN, PM_BATLOW_L and S5_PWRGD...
PM_SLP_S4 and s5 goes up to 3.3 for an instant when you plug in magsafe or when you short SMC_ONOFF_L then back to 0.
no chanhe on s3 that remains on 0
on the rtc my scope measures the 25mhz but they are not always present. 25mhz present for a sec, then nothing then back and so, 32khz are present and well stable
"PM_SLP_S4 and s5 goes up to 3.3 for an instant when you plug in magsafe or when you short SMC_ONOFF_L then back to 0."
So SMC so power button info to PCH and this one reacts too.
In this case, check if power supplies controlled by SLP_S5/4 pulse at least; should do it...
25MHz comes out only when board starts; or tries to do it.
Check again, better with o-scope, if SLP_S3 pulses at least.
That means even CPU VCORE tries to appear and PCH knows that.
Check now SPI termination resistors and traces around SPI chip U6100.
You can also try new BIOS.
3.3V at SPI chip means PCH doesn't access it.
There are 24 resistors, not 4...
Check U6101 too, resolder both chips.
Be sure no corrosion there, nor on U1950 area.
Do you get 24MHz oscillation at Y1915?