Laser moves but does not turn on from Lightburn, machine's test fire button works

To confirm, you’ve tried reseating the connectors? Specifically the one on the L pin.

Yes, I’ve also checked that if i pull the plug up slightly i still have continuity from the post to the other end of the L wire at the board. (If that makes sense, basically i had continuity from the LPS pin to the board). Yesterday i completely removed the L wire and reseated it.

Not sure what else it might be at this point. Granted there’s been a couple of surprises for me in terms of your laser.

The key will be in understanding how the remote test button is different in function than what’s happening with PWM signal on L.

Are you able to test the pins on the RJ-45 port on the LPS and test which other pins on the LPS they correlate to?

Also, when you use the Test button on the remote and turn the knob, do you get a wide variation in current on the display?

Also, I think you did confirm that water protection and door safety are being recognized and working correctly, yes?

I unplugged the RJ45 from the test button and lightburn worked. So annoyed lol

Also, yes i know the protections are working, checked continuity on those, and the lnob does show my normal range of mAs like 0 to 26 or so, but i don’t ever really go that high

I guess while you are here, it I’m getting more burn in one direction when cutting is it likely that my nozzle is angled? Thats my assumption, but just wanted a vote of confidence

How does anything lase without being pumped up with energy first? I believe these are used in my fiber to not only pump up the fiber but also to control the discharge duration.

The co2 is pumped by the high voltage DC, hence dc excited (pumped) laser.

Here’s the wiki on dpssl devices. Maybe you will interpret it differently. The wiki addresses some of these…

Maybe I’ve interpreted it incorrectly… You can read it, I’m anxious to hear your thoughts.

An inverted pwm of 25% results in a 75% on period. 75% of 5V is 3.75V – inverted 75% pwm is 25%, 25% of 5V is 1.25V…

This sounds like how they are controlling it. The voltages seem ok for an inverted pwm signal.


The only analog compatible input to the lps is the IN terminal… Anything else should be in a standard ttl control values.

I’ve watched these on my scope, the only thing that varies is the rms value of the pwm signal over it’s period, but it too is a 0 or 5V signal.

:smile_cat:

My understanding was that diode pumping refers to a specific technique where a diode laser is used to pump light into a separate crystal or similar medium which then induces that medium to emit light. Basically a two-step process. In contrast a direct diode laser generates the laser light directly. I understood these to be two distinct categories of diode lasers. So all DPSSLs use diodes, but not all diode lasers are diode pumped.

Additionally, my understanding was that the blue diodes we see are all the direct diode type, not DPSSL. I haven’t seen it documented but my assumption was that some of the 1064 nm diode lasers were DPSSL.

I could be wrong on all 3 accounts.

This video briefly talks about the difference:
Lasers - Direct Diode vs Diode-Pumped Solid-State (DPSS) - YouTube

I thought you tested that before but I can’t find reference to it now.

Does reattaching it bring back the symptoms?

Can you elaborate? You mean it burns more along X vs Y or something else?

You asked me to check before and i didn’t, at the time, sorry about that! I just forgot and was distracted by checking Other things. I just remembered to check last night, I’ll have to see if it Let’s me plug it back in later.

I am usually cutting leather and I’ve just noticed that to the left of every cut line it is darker with hard to coach burns left on the leather. Always to the left so generally the left side of the piece is nice and clean because the sheet gets that burn, but the right side of most pieces has a line that is difficult to clean at the edge. Sorry i don’t think I’m explaining it great, but that issue is why i was trying to better fine tune my alignment.

Sounds like you’re not getting the beam directly down the center of the nozzle. Place something directly at the end of the nozzle such that you can get an impression of the nozzle onto the material then run a test shot. Is the dot centered within the nozzle?

You should also check that the beam is aimed perpendicular to the bed. So run a test dot while the material is close to the nozzle, then again with the material farther away. The dots should overlap. If they don’t that means the laser is travelling at an angle.

Yes i have been using the center dot method to align mirror 3 but I’ll investigate the angle with that method, thanks! Just have to figure out the best approach to raise and lower material without adjusting x or y by accident.

If lightburn still only work with test button unplugged, is there much else i can do? I mean it’s fine if that’s the case, was just wondering if not having the ammeter was likely to be the new normal. Thanks again for all your help, i really learned a lot about my machine.

How is the material raised and lowered on your machine?

This implies there’s something wrong with either the LPS or remote. Were you able to confirm if pins on the RJ-45 correlated to other pins on the supply?

You could get an analog meter which may be preferable in any case. I’m curious, though, what the implication is for not having the remote plugged in since it was used to control max current. It’s likely that means you have access to unrestricted power but it could also mean the machine falls back to some default. I’m not familiar with how the remote communicates but running with the assumption that it’s fairly simple and directly wired to other pins on the LPS.

It doesn’t have a way to do that but I’ll figure something out

Nope, haven’t looked at all, that’ll be my next project i suppose

I’ll have to run some more test files to see if there is a relative difference in power

How is the laser focused?

There is a set screw that holds the end of the nozzle with the lens in it, and I manually adjust it

Got it. So I guess will depend largely on how concentric the components of that mechanism are.

Yes i definitely think that’s a factor, not an ideal setup but i wasnt ready to go all in on the real deal. OMTech going to send me another ammeter.

The laser may be slightly stronger without ammeter but not a dramtic difference.

Rj45 found so far
1 2 3 4 5 6 7 8
G IN - - IN - L P+

You said you checked voltage at IN and L while turning the knob correct? IN did not change and L was in the range of 1.1-1.3V which surprises me a bit.

So OmTech is sending you a new remote? Did they do any troubleshooting to determine that was the faulty part?

From what i remember yes, but i can check again later. Very confident that L did that, less so about IN. But IN shares continuity with 5V line, those RJ45 pins mark IN also had continuity with other 5V line.

They mentioned a couple responses in to try lightburn with it unplugged. Did a couple simple steps first, like protection, what is ammeter screen saying, etc.

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