HOW TO collection

2informaticos

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I hope this "How to" collection will help our members.
I will possibly modify this post in time, if updates available.

Trigger SMC_ONOFF_L (PMU_ONOFF_L):
It reffers to simulate power button function, when the keyboard is not connected.
We need to do this when we work with the board alone on the desk, or when we have doubts about power button.
Apple placed special pads for this purpose; as example, R5015/16 (3115), R5115/16 (00165), R5225/26 (00923), depending by model.
Newer models have some kind of switch pads (not populated), marked as RE030/31 (00850), or SWE10 (01521), etc.
Just search in pdf for "ONOFF"; easy to find them, connected to SMC_ONOFF_L, or PMU_ONOFF_L.
In fact, we don't really need to use these pads exactly.
Is very easy to solder a tiny wire on the pad corresponding to the signal; just touch any metal plate with it, when you want to simulate power button.
Just a temporar contact, of course.
When I really need to use it many times, I prefer to solder a small button, with 5-10cm wires.


Check PCH's RTC signals:
We reffer to DC signals, not 32KHz, or other PCH clock signal.
Intel platforms have 4 typical signals, RTC_RESET_L, PCH_SRTC_RST_L, PCH_INTRUDER_L and PCH_INTVRMEN.
Newer platforms, may not use PCH_INTVRMEN or/and PCH_INTRUDER_L.


Start in SMC bypass mode:
Press power button, maintain it pressed, connect charger and release the power button after 5-10s, or when the fan starts.
Fan will start with max speed, if succeed.
Used to discard SMC sensor problems.
It is very usefull, to discard a SMC sensor issue.

Start in safe mode:
Press Shift key and power button at same time.
Can help to diagnose if a problem is being caused by software that loads on boot.

Start the built in AHT:
Press D key and power button.
Very useful for the machines from 2015 and newer, as no ASD available since then.

Start from built in recovery mode:
Press Command + R keys and power button.

Start in target disk mode:
Press T key and power button.

Start in single user mode:
Press Command + S keys and power button.
Allows you to run terminal commands with full access to the file system.



Test in diode mode:
Connect positive probe of the multimeter (red) to ground and touch the test point with black probe.
Sometime (rarely) we need to test in reverse direction.



Enter DFU mode, for T2 machines:
Many people complain they can't acces DFU mode following Apple instructions.
Here is a link with detailed steps, reported as working.



Check USB activity:
The best and safest way (not cheap)
The cheaper way, using an USB pendrive with Link LED, like this (just as example)
I use 64GB with preinstalled macOS El Capitan, or 32GB with ASD (12 versions).



Disable GPU on some MacBooks Pro:
 
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