Wishful thinking but is it possible that the current pot / dial can break

Wishful thinking but is it possible that the current pot / dial can break so that it seems like the laser tube is dead? How would I go about testing my laser tube?

Laser just died while cutting, water flow was good and temp okay.

Desperately need a new tube, can anybody recommend a UK stockist?


If you have a multimeter, measure the resistance between the middle pin of the pot and one of the other.

If you don’t have a multimeter, disconnect the pot (at the PSU side) an connect the IN pin to the 5V pin (labels on the PSU). Warning: this makes it full power! You should then be able to testfire with the test switch.

I’d recommend Just Add Sharks


Thanks for the quick reply Claudio, really appreciated. I’m not too good with a multimeter so taken pics of what I’m doing. Does this mean the pot is okay?


Adrian, do you have one of their tubes? The 30W one I’m guessing? Does it fit OK?

@Adam_J Is there a cable connected to the middle pin? I don’t see one on the picture. Just turn the pot while measuring. It’s ok if the value changes between something like 0 and 500 Ohm (or 1kOhm).

My bad, I connected the wires and it seems to be working, changing between 0 and 500 Ohm.

Everything is working but no laser firing. I’ve read similar posts on here that suggest it could be the PSU. Laser power just disappeared middle of a job. Do laser tubes just die this way suddenly? Without specialist equipment, I understand it’s impossible to test the high voltage side of the PSU?

Well, I’ve ordered a new PSU and LightObjects replacement tube. I guess it’s going to be one or the other and it’s essential to keep spares. I’ll post which of the two it was for the records!

My pot was loose on delivery and is also inclined to turn slightly by itself during use, presume vibration? It seems incredibly sensitive and the slightest turn can more than double the power. Is there a better pot to fit?

You can replace the pot with a multi turn pot like this http://www.ebay.com/itm/1-3590S-2-502L-5K-Ohm-Rotary-Knob-Wirewound-Precision-Potentiometer-10-Turn-New/332212855800?_trksid=p2047675.c100010.m2109&_trkparms=aid%3D555018%26algo%3DPL.SIM%26ao%3D1%26asc%3D40130%26meid%3Da29b086576e940d2abeb1d7cb5091beb%26pid%3D100010%26rk%3D4%26rkt%3D6%26sd%3D262504968787

That looks perfect, so it can give really fine adjustment at the low end?

At least much finer than the original pot, and you can block it from moving.

Just ordered one, will be 3 weeks but I can wait. Don’t want to mess about before my upcoming event deadline anyway, too risky.

Ha it finally turned up today, that’s 6 weeks, and the connectors are marked differently to the standard one so now scouring the internet (in vain so far) for a wiring scheme.