Is the laser switch working?
If you read voltage across the switch when it’s active you should read 0V as it’s the same as measuring at the start and end of a wire.
I can’t really relate anything from the terminal block… except it looks like it’s feed with red that change to white or vice versa.
One of my pet peeves in life is having something start working without knowing why, exactly. The laser is now firing. The meter shows voltage. When I turned it on this time the meter started working. I turned it up all the way and burned a circle at 90%, and it showed 22 mA. It didn’t cut well, but the laser is firing.
I probably now have a mirror alignment issue because it didn’t cut well, due to the new tube installation probably. But I can take care of that.
So first, thank you all! And, do you have any thoughts about why it suddenly started working? Loose connection on the laser switch? Not sure.
I got 119 volts across the laser switch because when you pull the back off, the internal contacts come together, so voltage passes through.
I’m grateful for your help. You all are great troublshooters!
Ron
It could be anything… most likely you have or had an intermittent. Moving the wires to follow them might be a clue…
Did you have the power knob turned up?
Have fun
I did. I also tried adjusting it which didn’t seem to change anything. The power level was fully controlled by LightBurn.
Thanks very much for your help.
The key switch on my laser failed intermittently at first, so, yeah, it could very well be an intermittent failure inside the switch.
If that’s the case, the next time it fails, measure the voltage across the switch terminals. A bad switch will measure about 120 VAC, because the internal contacts will be open. A good switch will measure almost exactly 0 V, because the contacts will be closed and connect the terminal together.
Trust, but verify!
I presume you mean measure the voltage while the switch is intact - not with the back off. Is that correct?
Sometimes you just need to jiggle the handle and things start working again. I would agree with the others that a loose wire connection or a partial break inside the actual wire would all explain an intermittent issue, and also be difficult and annoying to track down.
I’ll take the win for now, and because of everyone’s help, I’m a little better prepared to track down the problem if it happens again.
Indeed. If the problem does come up again, I think we can help you narrow down which handful of wires you should investigate by jiggling, and perhaps pro-actively replace several of them at that time 
Yup, take your life in your hands!
A more sensible way would be to unplug the machine, disconnect the wires, and measure the resistance, but my switch was resolutely intermittent: any movement would jiggle it into the correct state.
I appreciate the advice and the focus on safety. Thank you all for your help!
Gentlemen, I have another question/issue.
I did replace my laser tube - the new tube is of the same dimensions as the old. My problem is that when I pulse it to see where it’s hitting on mirror 2 (the tube is about 1 inch from mirror 1), it is about 3/4 of an inch low. How hard should I work to shim the tube to get that into the center of mirror 2, or should I just use adjust the mirror?
I have been working on various combinations of shims on the laser tube and I’m not able to move the dot much. It is very low and to the right when I pulse it onto tape on mirror 2.
Your advice would be appreciated. I haven’t changed a tube before.
When I’m aligning it from scratch, I put a large board in front of m2 at it’s maximum range and move the mark so it hits where the mirror should be.
Then move m2 to it’s closest point and mark it. Then at maximum.
You should be able to hit that. Unless it’s extremely out, you should be able to correct it with m1 adjustments… My new tube doesn’t quite line up with center of m1, but I’ve aligned it and am using it.
Thanks Jack. I’m working on just getting it somewhere in m1 so that it fully reflects off that mirror. If I can do that I’ll fee comfortable adjusting m1. My mounts don’t adjust, so it’s all shims at this point.
Might be a good idea to replace them with ones that have screws you can turn by hand.
At least you’re gaining on it…