My stereo,Mach brand, on my 98 Ford Expedition Eddie Bauer, the stereo comes on ,it shows i'm turning up the volume, but i get no sound. I had a friend jump my vehicle and the cables were hooked up wrong, i heard a pop, and my volume has not worked since.

Is this a factory radio? First check alll of the fuses, fuse links inside and under the hood. There could be a couple of possible issues. When you hook up the cables wrong you ultimately send power to the ground circuits and ground to the power circuits. There are lots of modules in most vehicles and they are succepable to voltage spikes. There is a common industry term called "letting the magic smoke out" when this happens. If your vehicle has a body control module, it could have been damaged, the radio itself could also be a module and have been damaged. There could also be an amplifier that may have shorted out, this would explain the radio powering up but no sound. If you can get a wiring schematic and pull the radio you can check the inputs (power,gnd ,etc). If you had done this on a Nissan we would'nt be having this conversation, Nissan installs a safety relay on their vehicles that is wired in backwards and is only energized if the cables are reversed, this relay disconnects all of the sensative equipment/modules so they are'nt harmed once it is energized. I would'nt go out and buy one just for this feature, just food for thought.