Dead mid-2012 logic board? How do I narrow down?

KSUWildcatFan

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May 9, 2009
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Some history:

Bought my friend's mid-2012. It was running horribly slowly. Replaced RAM with Crucial 16GB (8X2) and confirmed it was working. Installed mojave to a solid state drive (via USB). Computer rebooted, things seemed fine, so I went to swap the drive in for good...

Buttoned it all up, now it won't boot. Only the light on the front comes on. No sounds. No keyboard lights. Fan spins. Nothing else. Tried swapping EVERYTHING back, to no avail. Tried resetting both NVRAM and PRAM. Nada.

I'm assuming I somehow killed the logic board but how do I confirm so I know for sure? Or, have I already?
 
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KSUWildcatFan

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May 9, 2009
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I'll give it a shot when I get home. I ran the battery dead last night by accident (fell asleep while messing with it) so I couldn't try this morning. I don't assume that'll change anything as I've tried swapping/reseating the RAM, but I haven't tried just running one stick. I assume the logic board is more than likely dead and unfortunately that means this isn't worth fixing. Bummer.
 

KSUWildcatFan

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May 9, 2009
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Well, scratch that..I guess my friend already tried that while I was playing his VR. Sounds like this thing is toast. Probably shocked it when I went to swap drives. Neat.
 

firelighter487

macrumors regular
Apr 30, 2014
161
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The Netherlands
Don’t be so pessimistic.

you can try unplugging things at the logic board that you do not need for the machine to boot, like the cable doung to the ssd, optical drive, wifi etc. See if it boots after that.

also reseat the cable connecting the screen. If that came loose somehow it will explain why you aren’t getting anything on the screen.
 

KSUWildcatFan

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May 9, 2009
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I'm getting absolutely nothing though. I put the old RAM and platter drive back in. When I power it on I get the fan which goes from slow to basically full speed (and then stays there) and the hard drive spinning, but nothing more. Still nothing on the monitor, no keyboard backlight, no caps lock when I press it, etc.
 

firelighter487

macrumors regular
Apr 30, 2014
161
12
The Netherlands
I'm getting absolutely nothing though. I put the old RAM and platter drive back in. When I power it on I get the fan which goes from slow to basically full speed (and then stays there) and the hard drive spinning, but nothing more. Still nothing on the monitor, no keyboard backlight, no caps lock when I press it, etc.
Does the power light come on?
 

KSUWildcatFan

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May 9, 2009
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Yeah, I think it's hosed unfortunately, given how it all played out. I'm dumb for not taking better care to avoid static while I swapped the drives. But I've done so many of these and never had a single issue. Go figure the otherwise CHERRY system I actually wanted to keep would be the one to drop dead. Ugh
 

Fishrrman

macrumors P6
Feb 20, 2009
18,030
5,977
The internal ribbon cable that connects the drive to the motherboard on the 2012 design is notorious for failure. Without proper communication between the drive and the motherboard, it's "looks to the user" like a bad drive or motherboard failure, but it's "only the cable".

Try replacing that.
Go to ifixit for the part number, then either buy it from them or elsewhere online.

If it still won't boot, I suggest you replace the new RAM with the factory RAM and try again.
 

KSUWildcatFan

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May 9, 2009
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Would a faulty cable cause it to not even beep (no sounds) when I power it on? Shouldn't it do more than it's doing with the cable unplugged (no drive present)?

EDIT// It sounds like that's what you're saying, I just want to confirm.
 
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firelighter487

macrumors regular
Apr 30, 2014
161
12
The Netherlands
Would a faulty cable cause it to not even beep (no sounds) when I power it on? Shouldn't it do more than it's doing with the cable unplugged (no drive present)?

EDIT// It sounds like that's what you're saying, I just want to confirm.
it should still POST and boot to either internet recovery or just give you a flashing folder that's like hey where is the drive.

that ribbon cable failed on mine as well, but it just resulted in slow speeds. I could still use the computer it was just horrifically slow.
 

KSUWildcatFan

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May 9, 2009
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Right, my thought exactly. When I bought it I was told it was 'beeping' and his research indicated bad RAM. not sure if it was booting or not. When I got it, it booted fine but was ungodly slow. I popped in the 16GB of ram and it registered but was still crazy slow. That's where I started the process of getting the SSD situated. But it didn't 'STOP' working until I touched that cable.

His original comment to me: "I have a MacBook 2012. Great shape but it’s doing the thing where when I boot it it does the beeps that when I googled that specific pattern it’s dead RAM. What can I get out of this? I wanna sell it. You want it? Or how should I go about it"

Still waiting on confirmation of whether or not it booted when it did this.. It always booted for me, it was just crazy slow.
 
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KSUWildcatFan

macrumors newbie
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May 9, 2009
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Ordered a new cable so I guess we'll see where that goes. If I flat out UNPLUG the cable from the board shouldn't it do something more than it's been doing? Or does the 2012 just..... NOT do anything if the hard drive isn't connected?
 

firelighter487

macrumors regular
Apr 30, 2014
161
12
The Netherlands
Ordered a new cable so I guess we'll see where that goes. If I flat out UNPLUG the cable from the board shouldn't it do something more than it's been doing? Or does the 2012 just..... NOT do anything if the hard drive isn't connected?
it should boot up just fine. I think you wasted your money... if you unplug the drive it should just post and give you a flashing folder icon indicating it cannot find a drive to boot from.
 

KSUWildcatFan

macrumors newbie
Original poster
May 9, 2009
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Yeah that's kind of my thinking also. Oh well, I'll try it when it gets here and then if (when) it doesn't work I'll part it out. Meh.