It could be a voltage issue. If you have a volt meter, the first thing that I would do is measure the input voltage to the unit. If that is good, then measure the output of the bridge rectifier. Sometimes they can partially fail which will cut your voltage in half. If that looks good then I would measure the voltage on the pins of the 5V regulator. You should see the bridge voltage on one pin and 5V on another. If you don't see the bridge voltage then you have a bad connection and if you don't see 5V, then the regulator needs to be replaced. If you do, then you need to look at the 3.3V regulator and do the same measurements. You should see the 5V from the 5V regulator and the 3.3V output. If you don't see the 5V input, then you need to trace back the connection. If there is no 3.3V, then that is the regulator that needs to be replaced.