How do you know it's the logic board? Mine was hard to tell as my 1st MBP doesn't boot from external HD. If I didn't bring it to Genuis bar, I won't know it's damaged.
To be perfectly honest, nobody is 100% sure it's the logic board, including the several Geniuses that looked at it when I finally gave up troubleshooting it myself (after two weeks of intensive troubleshooting). But the logic board seems like the most reasonable culprit. Here's why:
When recording audio (voice) via USB microphone when on battery power with AirPort turned on, two of the three USB ports exhibit unbearable levels of static in the recordings. Recording my voice is something I do frequently for work, so I ran into this problem fairly quickly. When plugged into the mains (or with AirPort turned off, or both) the audio is clean. Clean install of 10.4.9 seems to make it better at first (which meant I originally thought I might be dealing with a very weird software issue), but the problem gets progressively worse as recording continues. Updating to 10.4.10 makes it worse, and the most recent AirPort update makes it far, far worse---another reason I thought at first that I might be dealing with software problems. As it turns out, though, nothing fixes it.
The problem presents itself regardless of which microphone is used (I've tried half a dozen, of varying quality), which wireless network I'm on (tried three, at vastly different locations), and which software I use to record my voice. (I tried with Audio Hijack Pro, GarageBand, Adobe Soundbooth CS3, and then even Windows Sound Recorder running under VMWare.)
One of the three USB ports, though, gives clean audio recordings under all circumstances. This was the tip-off that the logic board is likely to blame, because the one port that works well is the one that's on a separate board. Both of the two bad ports are on the main logic board.
The static is really, really bad. "Wow" was about all the Geniuses at the bar could say. It looks like as far as the Web is concerned, so far I'm the only one on the planet with this specific issue, because a week's worth of internet research turned up absolutely nothing on this.
I'm a little worried about having them take the laptop completely apart, but given the kind of work I do (and the amount of money I paid), I can't just live with the problem, and I've had the machine too long to get a replacement laptop. I've got AppleCare Protection Plan on the thing, though, so if they screw something else up during the repair process, I guess I'll just have to be firm in making sure they make it right. I've got a second MacBook Pro (last-generation C2D 15") to use as a backup, until I'm sure the SR is 100% working.
They're waiting for the replacement board to come in and said I could just hold onto the laptop until it did, if I wanted to. Obviously that's what I did, so that's what I mean when I say it's going in later this week for repair.
