Why aren't my MacBook Pro's internal speakers working?
About 3 years ago I spilled milk on my MacBook Pro. It was fine until a few weeks ago when it wouldn't turn on. Genius bar said it would take $800 to repair. Opened it up and scrubbed down all parts with rubbing alcohol and let sit out overnight. Started from logic board with tweezers and I heard the startup chime. Booted up as usual and brought me to login screen. Keyboard was not functioning in certain areas, but the MacBook was otherwise normal. I plugged in a USB keyboard and that worked fine. Sound was working and everything was normal. However, the sound stopped working yesterday. No startup chime or anything, and when I went into system information, it said that no internal speakers or Microphone were present. It does not recognize headphones either. The internals are not corroded so far as I can tell. I've taken out both speakers and rubbed the connections with isopropyl alcohol. What could be wrong with it and how do I fix it?
This is what I see when I go to system information and go to the Audio tab: