Question: I have a Xermac CNC machine and the main computer will not boot up. The error indicates low power coming into the drive, but when I throw a volt meter on the output of the power supply it appears to be working.

Answer: You may be facing two issues. That machine uses a solid state drive with TTL logic. TTL technology is very sensitive to high or low voltage and can be easily damaged by high voltage. To accurately test the power supply you need to connect an oscilloscope to the output and view the voltage output. Some older power supplies will produce a “ripple” voltage when they go bad. This ripple sends a fluctuating voltage that a scope can see, but a typical volt meter would read as normal voltage. Some solid state drives, like the drive in your machine have a maximum high voltage of 5.25 volts. If the ripple voltage exceeds 5.25V it can damage the drive. So it is possible that your power supply is actually bad and if so you may have to replace the drive as well.