No sound except with headphones pluged in!?

Hello all, My wife dropped my iphone 4 in a glass of Mountain Dew and didn't notice for a good 30 mins. So i bought the kit to take it apart and clean it. To my surprise everything worked great. Then after a few months my phone started randomly shutting off. My fix to this was to take 99% rubbing alcohol and clean the entire motherboard. Upon putting back together my sound does not work. Ive replaced the Charging dock and speaker assymbly twice and done numerous other "fixes" so im thinking it has to do with me putting the alcohol on the motherboard. Which part controls the sound and what should i look for to determine the culprit? Any help would be much appreciated!