"50 SERVICE" means the fuser is not up to temperature. This is usually one of three things, the fuser element, the thernal cutout or the fuser power supply has failed. The element and the cutout can be measured with a VOM and should be < 20 ohms. The easiest way to test the PSU is to swap it with a known good one if you have one. There is a power on timer that takes a long time to discharge so it can take turning the printer off for 20 minutes to clear this fault. Lee.