[PNaedele]

Shop I work for has an FNC-128 with Fanuc 6MB control and what Makino was calling an 'UM15A cpu' for handling PLC related stuff.

Today the 5 volt power supply for the UM15A died and unfortunately I didn't check to see if the wires were labeled before ripping it apart so I have a 50/50 chance of getting the polarity right when the new power supply comes in. It seems like I have an incomplete electrical drawing for the machine, plus there's a whole lot of undocumented stuff that happened in the electrical cabinet over the years.

I tried looking for anything from Fuji who has their name on the circuit boards for this PLC and can't find anything.

Anyway the 5 volt wires go to the backplane on two wide traces that wrap around the outside in a C shape



Attached is a picture of the lower portion of the backplane. The two wider traces you see on the bottom. I could assume the outside trace is the (-) bus, but I'd like to try to make absolute certain of this.

So, does anyone know the polarity, or would anyone know where I could find out a little more about this PLC?

[PNaedele]

For future reference. The negative bus on the backplane is the outer trace.

Hooked up my new 5VDC power supply and she works.