When playing LP the sound is bass heavy, but when playing a cd, the sound is perfect.... any suggestions?

The record deck is played through a separate pre-amp to all other functions, so it therefore could be a fault in that pre-amp, but I doubt it. You can fit a wide verity of cartridges in record decks that will each give a different response to the sound. But first check that the cartridge connections are correct. Try swapping them around, it might change what you get. But it could simply be that you have a cartridge that produces a lot of bass. Changing the cartridge to a high quality recommended type - by say some hi-fi buffs website or magazine, might solve the problem.