MacBook Pro 15" late-2012 no input/output devices detected I did something silly. I replaced the trackpad in my MacBook Pro 15" mid-2012. It (for some reason) involved taking the motherboard out (via iFixIt's instructions). Everything works now, except the sound.

OS X reports no input or output devices. Nothing works, even when I plug headphones in. I'm not sure how OS X detects that a sound device is actually recognised, so I can't really troubleshoot the hardware. Any ideas?

I've tried all the usual, reset PRAM, SMC, etc.
I can't be sure, but I think that the first step to solve the problem is to check the connection of speakers to motherboard. Are they connected properly? Disassemble the laptop and check all the loops and wires.