[roofron]

need help with what causes the power supply to alarm on 04p-c control

[Al_The_Man]

What is a Fanuc 04p-c control?
Al.

[cnc2149]

The 04PC is an Amada with a 00-PC CNC control. If you are getting the Red LED lit on the Input Unit, then the voltage monitor of the CNC power supply is likely telling the Input Unit to shut down to prevent internal power supply damage. Normally, you can isolate the problem by shedding the various loads. Most of the time, it is not a bad Input Unit or a bad CNC Power Supply.

I usually start by removing the I/O C7 board from the master board. Most of the time, an external machine-side short circuit is pulling down the 24E supply so this will disconnect the machine side from the CNC side. If it comes up w/o the Red LED lit, re-install the I/O C7 board with none of the 5 Honda plugs connected. If it fails to come up, you have a bad I/O C7 board. If it comes up, power down, connect 1 of the Honda cables and try powering up again. Keep doing this until the machine will not come up to identify the shorted cable. Once you find the shorted cable, it's a matter of chasing the short on the machine side (e.g. bad cable, relay, switch, etc).

There can be more to it than I wish to explain here in the first reply (e.g. you can have an external I/O board hanging off of the PMC-M ROM board) but following the steps above is a good place to begin.