Hello, i am Giuseppe and i have an homemade CO2 laser, equipped by trocen controller (7813) and 40W CO2 tube (made by Sentech).
The problem Is when a job starts, tube doesn’t emit any laser bean outsider the tube Lens. But inside the tube i can see the tipical violet light going trought the tube. The stranger thing Is that ammeter reports more than 30 mA (go out of scale) starting from 15% of selected Power.
All connection are correct (the laser worked before) and controller works well, i tested his pwm signal.
In your opinion Is the tube exhaust? Is the laser Power supply broken? or…are they both broken?
I don’t understand… if laser tube Is broken, why current Is more than 30mA? Is It possible that Power supply Is broken and It pumps a lot of current and consequentially the tube doesn’t work’s too… ? Thanks for your support.
Hello Jack, tank you for your support.
The laser tube worked fine since 2021. In the past controller was an MKS DLC32, but same mounth ago i decided to change controller board, i need to engrave fast. So i bought AWC 7813 by trocen.
PWM of trocen Is on IN in laser Power supply, and TTL on L.
I know that current must to be not more than 19 mA for 40w, the fact that ammeter indicates more than 30mA Is very curious. Also i know that the quantity of current is not request by laser tube, the current is pumped by lps, for this reason i thing that lps can be broken and than It has broken the tube.
Now, current Is too much, laser beam passes through the tube but has no power outside the tube…And i don’t know if i Need a new tube or lps or both.
PS. I am Sorry for my english…
I had to look at another AWC controller for their labels. It appears it’s connected properly.
Without the laser power supply powered up…
check that the pwm is at 2.5V when set to 50% pwm
that L (ttl1) toggles – this is laser enable
If these work, I can only say that the lps is toast. Seems odd that a change in controllers alone would cause a failure like this.
When you loose a tube, most of the time, it’s an open circuit for the lps and the voltage skyrockets causing a discharge from the anode to the case or ground.
How you know the laser beam is there? Most of us can’t see IR.
Does the tube show any signs of life, such as the pink glow or is it like it’s not getting power?
Might want to ensure the anode isn’t shorting out anywhere, that would draw full lps current and may be responsible…
I had once a tube that had probably overheated, at low current (< 30%) it worked somehow, over that level there was the pink glow at the rated current but no IR.
My explanation is that the tube internal mirrors were no longer correctly aligned, and at high current were completely misaligned, which killed the cavity gain, so no lasing IR effect.
the overcurrent is weird, I have no clear explanation for that as the power supply is supposed to be quasi constant-currant…
Thanks for your answer. I think there was a malfunction of some discrete component. The consequence is that the power supply has lost some settings, intended as thresholds or references for the regulation of the current. For this reason, the laser source also broke later.
I have made the decision to buy a new laser source and a new power supply, which I will not use to test the old laser… so the mystery will remain in my thoughts…
Anyway, I use a slush machine as a coolant for the distilled water, with a temperature range of about 2°C (17° to 19°). Could this damage the laser?
At this point you’re likely going to have to pick one and change it out. There is little to test at these high voltages supplies. Of course, that also means there isn’t a good way to test the tube.
I have never seen these symptoms, which are a bit odd. It might just be a crap shoot – you got a 50/50 chance
I have already ordered a new 80w laser, and an 80w power supply. I could test the old laser with the new power supply, but I wouldn’t want to cause trouble. also the new power supply provides 24kv which is not good for the old 40w tube. I think I won’t go any further with the investigation…
Only when the tube gets larger do you need a higher voltage. I’ve run my original 40W tube (in a 50W OMTech) with the supplied 60W supply… and am still doing so with a new 45W tube.
Glass co2 tubes don’t start conducting until they lase, but then they limit the current (also limits voltage) available, so voltage isn’t an issue.
I have a voltmeter on mine and the lps has a high voltage placard of 28kV, but it drops down to about 12kV under normal usage at 50% power.
Current flow (or heat) is the main culprit and if you adjust your laser power supply (lps) for maximum tube current, it shouldn’t be an issue.
