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:

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Update:I received the keyboard and installed it. Still no sound/usb. I quit the sound driver and restarted the computer. I reset the PRAM and the SMC. I updated all software and I did a complete reinstall of the operating system, to no avail.

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Not sure what could be causing both sound and USB problems.

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I added an image of what happens when I go to system information and click on the audio tab. It knows that it should have internal intel speakers but it says that its value is 0, which I believe means that the Mac doesn't recognize that the speakers are connected.

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Everything else besides sound and USB is working fine.

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UPDATE: I just ran extended testing with Apple Hardware Test and it said "No Trouble Found". I'm not sure, but does that make it a software issue?

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Recheck your speaker to logic board connections.

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I rechecked the connections, but there was no change. Could it be a partial failure of the logic board? It would seem odd for that to happen after I cleaned everything with Isopropyl alcohol and left it overnight in front of a fan. I'm not sure what steps to take from here.

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Just cleaned the contacts with Isopropyl alcohol and no change.

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I ordered the keyboard replacement, which should be here Friday, I am wondering if that could be causing the issues.

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Do you see a red light in the audio port?

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No, and I checked with a plastic pick to see if any debris had flipped the audio switch on and it was clean. I plugged in and unplugged a headphone adapter several times and it had no effect.

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Hi,

I had the same problem, and I resolved it today. I had checked the speaker connections but they were all in tact. I ordered a brand new logic board and put it in today. When I turned on my computer the speakers worked great.

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Would it be possible for a USB sound card to fix the issue?

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Robert will be eternally grateful.
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