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Fixed output mA

Hi Guys,

I have a bit of an issue which i can't seem to work around right now. When the tube fires, at a higher percentage (lightburn) than needed, maximum current output is 4.5mA. This current occurs at 20%, 30%, 40%, 60% & 100%. I've been using the gerbil for all of 4 months now and this has suddenly just happened.

Things I have tried;

  • Replace Power Supply
  • Replace Tube
  • Redo wiring

Given this has happened on two tubes and two different power supplies i'm feeling there's something upstream of either of these - that brings me to the gerbil. I will note that the gerbil has started to act a little funny this evening (hanging, missing heartbeats... etc) but having shelled out $450 already i don't really want to jump to another part that may not be the root cause.

Thoughts / Considerations would be more than welcome because i'm tearing my hair out.

Kind Regards,

Tristram Chapman

I'm not sure I understand your problem but are you saying regardless of the % Power you always get 4.5mA?  You might copy your settings and paste them here using $$ command for review.

Hi HumptyDumpty,

Thank you for the response. Yes, that’s exactly what I mean. It is severely irritating.

I’ll post $$ when I get home however it should be noted that it was working without any settings changes two weeks ago.

I am hopeful I still have my m2 board kicking around so I can test if that resolves the issue.


Tristram Chapman

Hi Tristam,

You can hook up a potmeter (5kOhm) on the 5V, IN and Gnd terminals of the K40 laser Power supply. The middle of the pot goes to the IN.

Disconnect the MG from these points and run a laser cut process (fire button on)

Test the laser power now and see if you can change the current on the amp meter.

Pls let me know what you found



Cheers, Paul awesome.tech

Hi Paul,

Didn't have a pot handy so i've done this the easy way - installed the m2 nano i had floating around. Laser is back to functioning as intended though to be fair i have cut out many possible causes (Lightburn, Mini Gerbil, PWM cable... etc)

I'll fiddle around with the gerbil when i get a chance (i'm building a second laser anyway) but i'll have to shelve it until i get these orders out the door.


Tristram Chapman

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