Chinese Laser burning out chiller cable

[Nick Michalares]

I got a good one for you guys. Someone always seem to know much about these machines. I am an engraver technician and I have a customer who purchased an 80 watt chinese laser, has had it about a year, and noticed a steady power drop. Checked the tube and it had a crack in it, probably from shipping since it was new. Replaced the tube, but the replacement had a different connector. They talked back and forth with some folks here that sell them, determined how to connect it from what they said. when vector lasering a job at half power, somehow the water chiller cable, which I guess is real thin, would burn out, evidently from some power backing up into it or something? I wonder if anyone may have some idea of where to begin attempting to repair this problem?

[Dan Hintz]

When you say "cable", do you mean the power cord? If so, is it plugged into the laser or into the wall?

[Nick Michalares]

I guess it is a separate cable that comes from the laser power supply. I haven't actually seen the unit, but the owner thinks it was "feedback" from the other power system, since it happened while he was cutting with those parameters.

BTW, thanks for the reply.

[pete hagan]

There is a contact closure switch in the chiller that detects water flow and provides a closed contact to the power supply allowing the laser to fire. Similar to the safety switch on the doors. Look for grounding issues on the laser and the chiller. Better yet go ahead and run a chassis ground from the laser and the chiller to the nearest building ground. It may be the conduit running back to the panel, a copper water pipe etc..

[Nick Michalares]

Thanks, Pete. I will give that a try.

[Nick Michalares]

I got there and saw that laser, I have never seen a laser with an 8 foot tube!! That thing is a MONSTER!! It turns out the "cable" is very thin wire, like Pete says, it is for a safety switch that lets the laser know the chiller is operating. The new connector they used to connect the tube arced to the chassis. Once they taped it, insulating the connector, this problem would occur only when the laser was doing quick power on/power off cycles, like vertically engraving a mug. As the laser would turn on/off quickly doing the design, this thin wire would get hot, melt then eventually blow the 10 amp main fuse on the power plug. This machine has a transformer to change the 110V to Euro current for the laser. What a cheesy arrangement. The wiring on the ground circuit looks like a spaghetti bowl. I suggested he rewire the chiller cable with a little heavier gauge wire and try that, even put a fuse in line perhaps. I was very hesitant to get into the wiring without a schematic. I always try to follow the creed "try the easiest first" as it turns out this is usually the fix. Hopefully this will do the trick.

Thanks for the help, you guys are great!

[Dan Hintz]

Is this "cable" part of the high-voltage connection to the tube? If so, you had better make sure whatever it gets replaced with has a sufficient breakdown voltage on the insulation... getting zapped with 50kV sucks.

[Nick Michalares]

The cable going to the chiller is only a thin wire for a signal the chiller is working, I guess. It has a separate 110V power cable to power the chiller. the cable that arced to the chassis was the one powering the laser. Seems the round metal screw connector has some kind of voltage going through it, perhaps the 50kV you are talking about. They wrapped it with electrical tape to take care of that problem. Then they said it went out through this chiller signal cable. I guess for the money they spent on the laser, you can deal with a few problems like this! I told them to make sure they have a fire extinguisher and never leave the machine running unattended!!! I think they only paid about 4K for this thing. It has the kind of tube the engineer at Vision told me you can make in your garage! Maybe HE can make it in HIS garage, but I don't. think I could.

Appreciate your help.

[Dan Hintz]

A "signal wire" indicates low-voltage and low-amperage, like 5V or 12V at a few milliAmps... if it's getting hot, that means a lot of current (or a very high voltage) is running though that thin cable. Either way, it's a bad design... if the cable was meant to carry a lot of power but they used a thin wire, or the cable was not meant to carry a lot of power but an easy short allowed it to, both are dangerous situations. Wrapping it in tape is a bandaid that may get someone killed.

[pete hagan]

Before someone gets fried you need to make certain that both laser and chiller are powered in the same manner. If both are 230vt and running via the step-up transformer I would check that both are wired correctly for the mains (230vt into machine) What may be happening is that one or the other have somehow been wired with the chassis hot and you are getting current through the signal wire and the chassis. This is likely a contact closure type of wire where there should be no voltage present. water flows, switch closes and the closed switch "grounds" the signal to chassis. Try measuring the voltage from the chassis (ground) to either connection on the water flow switch. You should read little if any voltage. Also try measuring for voltage from any bare screw on the laser chassis to a building ground and see if there is voltage present between the laser chassis and the building ground. Do the same for the chiller.

Definitely think that voltage is going to ground somewhere.

[Dan Hintz]

Good catch, Pete... forgot about the transformer. I would first make sure the ground on the input side of the transformer is connected to the ground on the output side of the transformer...

[Nick Michalares]

Good catch, Pete... forgot about the transformer. I would first make sure the ground on the input side of the transformer is connected to the ground on the output side of the transformer...

the chiller runs off 110 V from the laser.
Luckily the guy running the laser is an electrical engineering student, so he was above me on this thing already. I will forward these suggestions to him, or get him to log in and see for himself. I was simply an advisor and observer, so . . .

I am a little cautious to spend a lot of time with something like this not being able to see the results over more than a very short term, i will let the customer and his operator do that. This guy impressed me and I believe he will be ok with it.

Thanks for the tips, sometimes it is easy to forget the obvious! It all looked wired pretty clean but who knows.