Looking for confirmation on dead tube

[Brian Leavitt]

Howdy folks,
Short version: I believe my laser tube is dead, but maybe I'm missing something. It's 6 years old, the connections seem fine, The mA meter registers when I hit the pulse button, but the tube does nothing.


Less short version: I bought this red/black "60 watt" 5070 laser in 2015; my first and only Chinese machine, and the only one I have with a glass tube. Most all my experience is with Universal and Epilog lasers. Oddly enough, I've really had no problems with it at all over the past six years. Last night the water hose supplying the laser tube sprung a leak which took out my Y-axis stepper driver due to the water leaking into the cabinet. The laser was still firing at that time. I ordered a new driver and today I found and replaced the tube where it was leaking. But after I got it buttoned up the laser will not fire. I wired in a mA meter a few years ago and it still registers normally when I hit the pulse button, and the "Laser" light comes on on the power supply as well, but I can't see the tube lighting up at all and get zero activity at the lens carriage end.


I'm not sure what I could have done to cause this. Maybe air getting into the system caused it to overheat? My flow sensor is fine so I know water was flowing, but when I looked in there this morning there was a decent amount of air in the tube.

[John Lifer]

I would look closer at the other connections. You might very well have a short causing the tube not to fire. I'd really not expect that tube to die unless you let it run for a long time with no water. I'd bet the line headed to the tube might have some water in it or near. I'd be tearing more apart before I bought a new tube.

[Kev Williams]

concur - in the past there's been many a post on re-soldering/connecting the wires to these tubes...

[Brian Leavitt]

I would look closer at the other connections. You might very well have a short causing the tube not to fire. I'd really not expect that tube to die unless you let it run for a long time with no water. I'd bet the line headed to the tube might have some water in it or near. I'd be tearing more apart before I bought a new tube.

Would the mA meter be registering normally if this was the case? It's showing the correct mA reading for the various power levels I've set it to. I've got continuity to and from the laser tube on positive and negative wires.

[John Lifer]

I would assume so. meter is showing power headed to the tube. But check tube closely, if it did run dry, you might have a crack. I'll assume you have some color in tube when it is off..... If not and you did, then you probably have damaged tube.

[Brian Leavitt]

I've now checked over every connection and piece of electronics. I can't find anything wrong with anything but the tube. So I ordered me a new 60 watt EFR tube and power supply. The current tube is 50 watts so I'll have to make an extension housing since it'll be sticking out the side of the machine. But... I've been wanting to pick up an EFR tube for this thing for years anyways. Other than it lasting much longer than I expected, I have been thoroughly unimpressed with the tube that came with the machine. Of course, that's comparing it to a ULS or Epilog laser. We'll see how EFR compares.

[John Lifer]

the 80 watt EFR that is in mine is coming up on 5 years old. I've kept it under 30 mAmps which is about 75% via rdworks. I usually do my best to stop at 65% on almost everything, occasionally go up to 70%. So far so good. It stops firing at 17% on the bottom end which precludes me from doing some delicate items. But it works.

[Kev Williams]

Sorry I wasn't much help, but in 20 years the only tube I've ever lost was totally obvious, and it wasn't actually the tube (Synrad) but the RF electronics. My only glass tube is the 80w RECI in my Triumph, which will be 8 years old in November, still hasn't lost a step knock on my head.. FWIW it hits 26mA at 72% entered power, that's all I've ever taken it to during cutting, sometimes 75% when engraving wood. It fires fine at 8%, and I do test runs on thin clear acrylic for alignment checks at 6% but it's not consistent that low. I've nothing bad to say about RECI

[Brian Leavitt]

I appreciate the input from both of you gents. I would have considered RECI if they made a 60 watt tube, but as far as I know 80 watts is their lowest power option and I really have no need for 80 watts. I'm excited to get this EFR tube going, though. I got the 1200CL, which I've been eyeing for a few years. I also got the EFR power supply to match. The power supply has already arrived, but the tube was held up in customs because of some missing paperwork. It's now due to arrive Monday.

I wired up the power supply and tested it out. Seems to work fine. It came with a little display with the potentiometer to adjust max mA on it. The only thing I'm a bit concerned about is the mA on the display does not match my analog mA meter when firing the laser and I do not know which to trust. Max recommended current for this tube is 22 mA. If I fire at 99.9% with the mA meter reading 22 mA, the EFR display shows 19 mA. On the low end, when the mA meter shows 5 mA, the EFR display shows 3 mA. So that's a little annoying.

[John Lifer]

Unless you need full power, I'd trust the mA meter, your more expensive meter is going to be more trustworthy than a display meter. I'd bet they are +-10% accurate. Mine shows +-2.5% on the meter face. That would be .5mA at 22.

[Brian Leavitt]

That's the plan. The tube actually arrived early. And I finally bought a legit cooler. Past six years I've just been using an igloo cooler with an aquarium, pump. I just have to make an extension housing for the machine now since I've been unable to find one online.

[John Lifer]

I expect you'll have to make a box. Get some aluminum which would bend easier than steel. Pop rivets. Should be pretty simple. BTW, I've been using a killawatt meter on my equipment recently to see just how much each is costing me. The CW5000 chiller, in a roughly 75f ambient room is costing me a penny an hour to run. This is mixed engraving and cutting, but that's cheap. My chinese exhaust fan is about 2.5 cents an hour.
Cheep

[Brian Leavitt]

I actually have some sections of round steel bollard that I think are long enough to cover the end. I was thinking I'd weld a section to the extension cover plate from the machine and then just weld on an end cap. The only thing giving me pause is the weight. Those bollard sections are .25" thick steel which obviously is a bit overkill for this task.

That's interesting info about the running cost of the cooler. I had looked at getting the CW5000 several times in the past. In the end I bought the 600 watt cooler from Light Object since I'll never be running more than a 60 watt tube.

Oh, and after removing the laser tube from the machine, I did find it was cracked and water had gotten into every part of the tube.

[Kev Williams]

** this is just an opinion **

If I were putting a longer tube in a machine that was going to stick out and needed to be covered, I would make a clear cover out of 3/16" plexiglas. It would serve the purpose, much lighter than a steel box, and for fun you get to watch the laser fire

[John Lifer]

Yep, that would work, and be pretty cool. I don't think I'd use steel tubing that heavy. You might even bend the rest of the panel