K40 wiring problems

K40 with grbl mini board and LightBurn

Start up: power/light switch does not work, switch laser on laser homes and is ready but ammeter reads 20 amps and power switch/light now works. Ammeter reads 20 amp but reduces to normal when cutting.
I have had to replace the LSP and purchased stock K40 replacement. All wiring is as original but now power on switch only works once laser is activated and this turns on laser beam and power switch now works.The laser works but does not stop after cutting and remains on continuously. Any suggestions please.

Wow thats a mouth full.

Lets start with:
Pictures of your

  • Control panel
  • Controller
  • Connector side of laser power supply.
    Model # of your controller.

1.) What do you mean by “power light switch”?

2.) Are you saying on power up the gantry homes and then the laser turns on and reads current (probably 20MA not amps?)?

3.) Is this what is happening?
The laser comes on and stays on with power to the system, it will run a job ok but after the job the laser stays on.

4.) How is your controller connected to the LPS?

Please use the question #'s in your response

Thanks for reply. I have now sorted power switch problem so this is what still happens:
Turn on laser, lightburn connects and laser homes but laser is on running at 20MA. Can run job at normal laser settings OK but current returns to 20MA and laser stays on.
your question 3:yes
your question 4: connected with pwm lead from mini gerbel controller as photo.![IMG_0060|375x500]

I think Don would need pictures of your actual machine, not stock images :+1:

1 Like

Seems image did not upload will try again.

Let’s use this drawing to identify connections on the LPS:

Ignore everything but the pin numbers for now.

Where do the other ends of these wires go:
1a. P2-1(black): ?
1b. P2-2 (white with black housing):?
1c. P2-3(white):?
1d. P2-4 (red):?

  1. Where does the brown wire that it disconnected and taped go to?

This is how I understand the problem:
The laser comes on and stays on any time power is applied to the system

Try this test.

  • Power off the machine
  • Unscrew P1-1 from the connector and let it hand disconnected (the rightmost pin on the LPS)
  • Power on machine
  1. Does the laser still come on and stay on with the power.

Please answer refernceing these #'s

First thank you for your response. In desperation and knowing that all wiring was exactly as original connections I removed the mini gerbil board and replaced original M2 Nano board. Works perfectly so was obviously a fault with the gerbil mini board.
Sorry to have taken up your time.

So you have not been able to make the mini GRBl board work?

Purely from the symptoms here are some guesses:

  • If the laser is on with power on and no job running the L pin is being held low (0v)
  • LPS-L signal is somehow inverted. This means that when power comes on the LPS-L signal on the LPS is low (0v) but then becomes active with the job.
  • Laser Test Button and Laser Enable switches are wired backward on the LPS.