It sounds to me like you have a bad power supply board. Some component on it has gone bad either a cap, resistor, diode, or even a fuse. There are various components on the board that need to be tested. If you are familiar with soldering and desoldering, then go ahead and remove each piece and perform and ohm test as well as resistence test. Check relays as well. Most of the time one or more components on the HOT side of the board go bad. This can be time consuming so I find it easier to simply replace the entire board.