I am new in this forum and I am an old owner of this device. It seems that some of you have had the same problem with the sound. Sometimes, this problems comes with Tomtom 6 but another times the problem is the device itself. Take care using the 2.5 mm sound jack. If you use it, you can find that after unplugging it, the speaker does not work. In my case, the problem was that this jack uses to get jammed. Solution: to dismantle the pda. Even doing this, you will need a dose of luck because the jack is welded to the main-board, so to unlock it is not something very trivial. I tried with a pin, moving all the mechanisms inside the jack and I did it. This happened two times till today, the first time it was not necessary to dismantle the pda, I tried moving the components of the jack from "its natural" access and I was lucky, the second time I needed to open the device. If you decide to open the device, you will need to free the 5 screws (one is under the warranty seal) of the back side. Then to open it slowly starting with the top. Take care with the vibration engine, it is linked to the back cover and the cables that connect it with the mainboard are very thin.
Hope this will help and sorry for my English