MacBook Won't Power On After Repair

Hi everyone,

I recently bought a MacBook which needed a new display.

I knew the MacBook worked before hand as I had tested it before I disassembled it, and sure enough, the display was glitching.

Fortunately, I did already have a spare display for the right model. The issue was that I had a space grey display, but the MacBook was silver.

Luckily, I also had a spare space grey top case sitting around, so I planned on putting that on and essentially converting the laptop to space grey. I knew the top case worked, but I did not know if the display worked or not, so I took a gamble.

I was aware I may need to buy a new display in the case that the one I already had did not work, but I thought it was worth testing as it all looked to be in decent shape, with no visible damage to the T-CON board, and no visible damage to the LCD. Because I was unsure about the condition of the display, I decided to test the display before completely rebuilding the MacBook, which would take an hour or two.

What I found was that after plugging the MacBook into a charger, and pressing the power button a few times, I could get it to play the boot chime, but it would cut off halfway through with a speaker popping sound, then it would try to start again. Same thing happened 3 times, at which point I knew something was wrong, but I assumed it was because I hadn't plugged everything in as I just wanted to test the display.

My first mistake was being lazy and not testing it with everything plugged in. I carried on with the repair, taking the silver top case off everything, and reassembling the MacBook in the space grey top case.

After I eventually finished assembling the MacBook, everything appeared to be alright, but then when I plugged it in and tried to turn it on, nothing happened.

At first, I assumed that it was just the usual thing that happens when you plug in a MacBook after a repair; it takes a bit of persuading to make it come on - you have to plug it in and press the power button a few times before it responds.

I then noticed that the touch pad was clicking. I thought this seemed strange as it was seemingly the only sign of life in the MacBook.

Once I had unplugged the charger and opened the MacBook again, I noticed that the heat pipe was slightly warm which was weird as it had been on no longer than a minute, and the fans were spinning, but not normally - the fans would spin up, then stop. This would repeat every 20-30 seconds of so (I didn't time it, but it seemed like about this long). This must have been similar to the boot looping I had earlier where it would chime and then stop again.

I unplugged the battery, and I couldn't figure out what was going on. I tried unplugging the display as I wondered if there was a short as I was not sure about whether this display would work or not. I unplugged the display, plugged the MacBook into HDMI and tried again, still nothing, but I did notice that the TV 'No Signal' message would disappear when I pressed the power button or a key on the keyboard, but then it would come back. This too seemed to be related to the boot looping.

I tried unplugging everything from the motherboard other than the power button and the battery, but nothing worked. Same issue every time. After this, I thought my best bet would be to put the old display and top case back on as it all worked with this on before I started to close things up. I figured it could've been something to do with the battery. So, I got to work completely undoing hours of work, until finally, it was complete - the MacBook I had just 4 hours ago.

I went to plug it in, but this time, instead of working, it had the same issue as before, where it would boot loop but not show anything on the display or Touch Bar. Just to be clear the track pad could be clicked; the fans would spin up and turn off again and the CPU was clearly producing heat. Nothing else worked.

I am trying to figure out why it isn't turning on and if it is a logic board failure like I am thinking.

I would also like to know what your recommendations are to make it work properly.

I have tried both SMC reset and PRAM/NVRAM reset many times, to no avail.

Thanks,

Philip.