Update: Benz has clarified that the behavior of his machine turned out to be due to some kind of software conflict, making it more reasonable that no-one had suspected zero brightness earlier.

What appeared to be a major MacBook Pro problem resulting in $10,000’s worth of warranty work finally turned out to be a ridiculously simple fix taking seconds and costing nothing at all …

Photographer and developer Greg Benz tells the story.

My laptop “failed” again for the 4th time today. The first 2 motherboard replacements seemed odd, but I was given a completely new laptop from Apple on the 3rd failure. Just like before, the screen was pure black after clicking the power button and there was a slight fan sound. The only other indication that anything was alive was that the machine would still make an audible chime when plugging in power and the capslock key light could be toggled off and on. So after losing about 2 weeks of my time, >$10,000 in Apple warranty repairs (2 logic boards, new cables, and a complete replacement of a >$7000 computer), troubleshooting input from several Apple Geniuses, level 1 and 2 tech support from Apple Corporate, diagnostic tests at the Apple Store, and diagnostic tests twice at Apple’s repair facility in Texas; what was the root issue?

You’re not going to believe it:

The screen brightness was turned all the way down (not merely dim, but off).

The MacBook Pro problem didn’t, in fact, exist.

The backstory here is that Benz works on an external monitor, but says he’s had problems in the past using a Mac laptop in clamshell mode, with glitches causing them to sometimes sleep. So he routinely leaves the machine open, but turns down the screen brightness to zero (backlight fully off) to avoid distraction. He then shut it down for use while mobile. When he restarted it, it appeared to be dead.

The reason for this is long-winded, but essentially because Apple apparently never thought of this scenario, so made some decisions which would screw things up in this edge case.

The screen brightness at bootup is the same as whatever it was when shutting down the machine before. If you completely black out the screen when you shutdown, both the Apple logo and login screen are completely black at startup (no back light at all, even if you tried to view in a dark room). The brightness is only increased to a minimum value AFTER you log in. While most people probably don’t turn their screen completely off, I do so routinely when I have the laptop connected to an external monitor (I leave the clamshell slightly open to avoid going to sleep, as I’ve run into glitches there before). I also turn it off when leaving the room and the computer has restarted due to an (unrelated) kernel panic while unattended a few times this past year. This same completely black condition is allowed when running recovery mode, target disk mode, etc at boot. So none of the normal troubleshooting will turn on a monitor that was black last time you used the computer. The brightness control on the Touchbar is not available until after login. So there is no way to turn on the screen during boot or login. And a completely black Touchbar further suggests that the computer is not working. It’s not the sort of detail you tend to watch closely during boot and would remember when things go bad. External monitors are disabled during boot and login. I had tried these and Apple support recommended it as well. I can’t think of any security reason why external monitors shouldn’t be allowed for login (and it would be so much more convenient when working with a docked laptop so you don’t have to move stuff around to open the laptop just to log in). An external keyboard cannot be used to change monitor brightness during login screen (even the Apple USB keyboard) . The keyboard key lights are always off during login, even if they were on during last normal restart/shutdown. The Apple troubleshooting guides are out of date. They do not note that if you have a firmware password on a T2 Mac, you cannot reset PRAM as expected and therefore cannot resolve screen brightness issues this way. You also cannot run diagnostics due to the black screen. And lastly, they should probably ask users to try to log in blind knowing this list of shortcomings above. [Note that I use and recommend firmware passwords for security reasons, including to disable a thieve’s ability to turn off “Find my Mac” by simply holding down a few keys during boot.]

The problem was finally diagnosed by a Genius who was clearly thinking laterally.

He used the flashlight function on his phone to shine on the laptop screen and could see a little circle where your login avatar would show (and this was incredible difficult to see). It turns out that the screen pixels are updated even when the backlight is off (at least if the clamshell is open).

A blind login worked (type the first letter of your login name, hit carriage-return, type your password and then carriage-return again).

Is this the most obscure MacBook Pro problem ever reported, or can you beat it? Let us know in the comments!

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