Diagnosing a Bad Fadal Amplifier

We run Fadal CNC machines and Mayfly Manufacturing. They are solid machines and spare parts are readily available from 3rd party suppliers. The other day we got an error message saying "Error #18 Y-Axis Amplifier Fault". The message came up randomly during warm up cycles, machine cycles, and in jog mode. We lowered the rapid cycle to 25% and re-seated the cables going from the amplifier to the motor. The error message was still coming up. We knew the problem was from the amplifier, cables, or motor. We then swapped the x-axis amplifier with the y-axis amplifier. After we swapped the amplifiers we were getting the error message but now for the x-axis. Easy to say that the problem was coming from a bad amplifier. We ordered a brand new amplifier to replace the bad one and were back up and running.