Having worked at a repair / retail / custom install company in the past, and talking with the repair techs, I would just like to add that a lot of brands require a specific sequence to get into the service menu and resetting the EPROM is an option in some cases. I believe that Sony and RCA are both part of this category.

Try to keep track of the order of the codes you tried and post those as well, and if you experience a service menu, don't automatically think that turning the unit off will get it back to normal, power off and back on may just be part of the sequence to do something you don't want.