K40/mini - working system no longer works after 6 months of being ignored

Machine: K40 - with replaced “Z” bed etc

Board: C3D Mini (order # 886 - old…)

Firmware: both “whatever it came with that worked 6 months ago” and “Batch3 from C3D Dropbox”
Digital power level is set to “30”, which via prior calibration equates to 15mA on the analog meter.
Laser is “Enabled” on control panel

Problem/ Question: After ~6m hiatus of not using a tuned and happily working K40/Mini system, I cleaned it off, verified coolant flows, cleaned mirrors (etc) - and tried a test cut, which went thru all the correct servo-motions, but the laser didn’t fire at all.

Pressed TEST on the control panel - nothing. No laser tube activity.
Checked wires (all seated, no obvious issues), tried Power Supply’s test button - success! Tube lases as desired!
Checked forum, found reference to newer Batch3 firmware, tried it, no change - no panel- or LightBurn-initiated laser tube activity.

Any debugging clues out there? How do I make my K40 love me again? :slight_smile:


Hi John,

The mini has no control over the test button, so it is possibly a problem elsewhere, but first, let’s look things over.

Can you snap some pics of the electronics and tube compartment? Would like to see the components and wiring.

Do you know if your unit has a water flow switch?


It has a water flow switch, but it ties in to the laser P/S, and seems to work…
I’m going to be offline (medical) for a couple of weeks, and will need to let this thread drop - thanks, and I’l revive it when I’m back.


Water switches have to be tested because they can fail and you won’t really know it other than the laser won’t fire unless you hit the button on the power supply.

Get well soon, hope everything goes ok.

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