(page still being written)
If you have a macbook with no power, the first thing we want to do is head to the Power Alias page on the schematics. We need to figure out what rail/s is missing. There will be many power rails required for the machine to boot & different lines will be required for different power states.
For example if a machine is sleeping, your not going to want the CPU on, but your going to want the RAM on so it saves whatever you have running, therefore you don’t lose any of your work. But when its off you don’t want the CPU or RAM running but you do want the battery to still have the ability to charge.
PPBUS_G3H . ~8.3v
PP3V42 – 3.42v (used for the one wire circuit in order to give you a green light on the charger)
Intel Power States
PP3V3_S0 – Rail is present when the machine is machine is on
PP3V3_S3 – Rail is present when the machine is sleeping
PP3V3_S4 – Rail is present when the machine is hibernating
PP3V3_S5 – Rail is present when the machine is off but charging
In order to get voltage on the S0 rails, we need all the rails below it to be present. This same rule is applied to all other power rails. If the machine is in a S3 state (sleeping ), we know that we have S4 and S5 rails present..because we need them to produce the S3 rail. If we have S4, we know we have all S5. If there’s an issue on the S5 rail and S4 is not being produced, then we know we don’t have S3 or S0.
Lets battle test this.
Q7860 is what’s called a transistor. (a semiconductor device with three connections, capable of amplification in addition to rectification.)
On this type of transistor when the power on the gate (pin 4) is lower than the source (pins 1,2,3), then the transistor will allow the 5V to flow through to pin 5 and become PP5V_S0.
It’s basically like a light switch but we’re controlling it with electricity.