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.
Board symptoms- No sign of life at all. No shorts on any 5V-3V3 S5, S3, S0 rails. No fan spin even when attempted SMC bypass. G3H voltage 13.23V. Draws about 1 watt from wall in regular or SMC bypass mode.
in the process of measuring voltages I realized that u7200 gets very hot and board now draws 3w and doesn't have green light. I might have tapped two pins together to cause this but I will replace U7200 and update after.
edit: replaced u7200. board not booting same as before but u7200 not getting hot anymore so I assume my touching two pins shorted u7200. green light is back.
Voltages on new u7200-
16- 13.4v
3- 4.2v
8- 0.03v
17- 13.4v
1- 0.01v
6- 3.7v
I actually was measuring the voltages of U7000 not U7200. Sorry for wasting your time on that. Here are the correct voltages.
The chip next to it, Q7221, was also not getting any voltage on any pins.
Posted below are working, powered-on board voltages and dead board voltages on the right. so the difference is pin 1.
1- 1.26, 0v
3- 2.13, 2.2v
6- 0.87, 0.84v
8- 3.66, 3.65v
16- 13.8, 13.86v
17- 5.61, 5,52v
I do not have a scope, but there is no voltage on this rail no matter what I do. Tried measuring while I plug in board and also when I subsequently connect poweron pads and in SMC bypass mode.
Also it seems like SMC bypass mode isn't even registered. Even when poweron pads are connected while charger is connected, there is still a green light and the board draws 1 watt immediately. Normally in SMC bypass mode the green light stays off while the button is held and the board doesn't draw power until the fans turn on.
Be sure SMC_ONOFF_L stays high (3V).
When you trigger it (temparary shorting to ground), check for drop pulse at PM_PWRBTN_L (at same time).
No need to use oscilloscope.