@tyler_hallberg is the “test” switch on the panel good. Short across terminals or disconnect and measure with meter.
BTW that diode needs to go back in the right way round :).
No only test switch on psu works
@tyler_hallberg By above I meant to test the switch on the panel 
i.e test the “TEST” switch by shorting out the terminals and see if that fires it …
Showing out the test switch terminal for the panel and shorting out the L pin on the psu neither fire the laser
Shorting
Are you using a non-stock exhaust? And if you are, did you open the lid at all while it was engraving? I ask because I had an issue that looked exactly the same and it was caused by opening the lid a tad to peek, and the change in pressure (I’m assuming) caused the x carriage to skip. Once I stopped cracking the lid, I stopped having the issue.
@tyler_hallberg pls post close up pictures of your LPS. Show the edge connectors and also show the board where you removed/replaced the diode.
Pictures of the power transistors might be helpful as well.
Insure that the interlock circuit is closed. It is different dependent on the LPS type.
By “shorting out” the L pin I assume you mean you grounded it.
Sorry did not short out the L but did give it power as that’s how I had it running at one point with my Smoothie. I’ll post pics shortly
@tyler_hallberg note: the L needs to be grounded to fire. Assuming the interlock circuit is closed.
I hooked it up multiple different ways on the Smoothie board as well as swapped in the old circuits to see if I could get it working. Nothing made it fire. I’ll post pics in a couple minutes of the board
Test switch that does work
Stock board that has the test switch that does not work
@tyler_hallberg ah this is not a standard K40? Any schematics for that control panel board?
It’s the new “upgraded” version
Found my problem. Factory water flow switch took a crap. Shorted the two pins and all works great.