within the jack that opens up the speakers when the jack is plugged it. This contact may be staying closed.
Can you get an eyeball on it? It will be obvious and it's function will be seen if you can get to it. To replace this jack will be a pain as they are usually soldered to the board.
a while ago I had a problem about my headphones not working (I had a dodgy sound port). but I found out that if I twisted the plug a little I could make it work normally. but, as of today, my speakers play sound as my headphones do, and I'm very annoyed with the whole situation. thanks