If you hold the power button down when it is doing this, does it start up normally?
My very first board repair would do this, and you held the power button down, and it would start normally, ended up being a bad ISL.
Had another machine that would do this, and power on normally if the power button was held, and it was a short on a trackpad subrail.
Try it and report results. If the same, check for a short on S0 and S3 rails.
If the USB stick flashes, means the board is working in that time.
Check if board stays on if you start in SMC bypass mode.
Be sure heatsink is properly fixed and CPU/GPU don't get overheat fast.
Yes 27/28 is 20 ohms 17/18 is 3.8 ohms I notice something strange looking around u6100 I saw on a resistors smc_batlow_L fluctuating with power on its goes up to 4.9 and off but I have no battery plugged in. To my understanding it only goes high when a battery is pluggedThis will likely suck.
Recheck current sensing on pins 17/18 27/28 of the ISL should be 3-5 ohms / 20 ohms.
Also, resistance to ground on CPU and GPU VCORE.
Give me a few I check both cpu/gpu vcoreThis will likely suck.
Recheck current sensing on pins 17/18 27/28 of the ISL should be 3-5 ohms / 20 ohms.
Also, resistance to ground on CPU and GPU VCORE.
SMC batlow should go high with a battery or the use of a 85w charger. 4.9v isn't right. That is a 3.3v signal. Are your meter batteries low?
That reminds me. Are you using a real 85w charger with this?
When the fan spins, does PLT_RESET_L go high?