3D board in unknown 50W machine

Machine: 50w
Board: Nano M2 but has separate stepper controllers

Firmware: what came with machine

Problem/ Question: Just got another 3D board all the wiring looks straight forward but I have an extra 3 pin plug ? Sorry cant post picture yet . it’s labelled 5v, G, L,Red,Black,Blue any ideas how I connect it or do I not

Post some pictures of where it’s connected and your machine in general and i’ll have a look.

I cant upload pics. Have you an email I can send it to

I think I have figured it out ? It seems to be the 5v supply to the board to power it, I disconnected it and nothing worked except the X and Y motors resetting to home