Damaged Powerbook


My son's roommate spilled lemonade over his 12" powerbook g4 keyboard which promptly died. After apple quoted $900 to repair it we bought a new one but I thought it worth checking myself and had him ship it back home. When I got it and powered it up it started and went as far as the login screen before shutting down. The keyboard was trashed, but when I removed the upper case it showed no sign that I could see of any leakage. I've replaced the keyboard but cannot get it to boot up. The power supply cord is flashing yellow with the battery installed, or fixed yellow with it out. Suggestions as to what to look at?