Laser Power Has dropped off significantly. WTH happened?

[Cflanagan]

Marco,

As you know, I recently purchased a new 60W Laser Tube and a new 60 W power supply. Had everything hooked up and humming along perfectly. I've invested in a UPS to filter the power and insure there are no spikes or sags. Also have water pump set up and working perfectly. I had been cutting 1/4 plexiglass and the laser was performing perfectly. All of a sudden, the laser power seems to have dropped off significantly. I'm also noticing that the blue LED ammeter is oscilatting even when the laser is NOT firing. It had been showing 0 previously, now it's constantly moving from -.9 (NEGATIVE) to +1.4 and every number in between.

No major events, checked the fuse on the Power supply, No Zaps, arcs, no burnt wiring. Nothing eventful happened at all, just all of a sudden the power dropped off. I have the software and dsp set at 50% power, even now when I fire the laser its typically showing between 19 and 22ma (I've been VERY careful about not overdriving the power supplly) but I can tell the laser beam is not as bright as it was. I have the tube encased in a PVC pipe with foam around it and a window cut out of the pvc so I can see about 12" of the tube.

Checked all wiring, connectors, Water pump is running fine, The tube hasn't been run dry even once. Again, all was humming along perfectly and all of a sudden, major drop off in power. I'm lost here, I have no idea what happened. Is it possible this is a bad tube? Or is it another power supply issue? Not sure how to trouble shoot this.

FYI - I'm only doing short run cuts, maybe 2-3 minutes of lasering, then 30 minutes to a few hours during which I turn the machine off, so i'm quite sure i'm not overpowering or over heating (I can touch the tube and it's room temperature or cooler, the water is not getting hot since the laser runs are so brief.

Can you help me with this? I'm in the middle of a job and I need this thing running asap. I feel i've checked every thing short of pulling the tube out of the PVC housing which I really don't want to do unless absolutely necessary.


Thanks in advance for a quick response.

[Tech_Marco]

It look like to me that the connection to the digital meter may got lose. Check there first. Then, you may bypass the current meter see if it works.

The other problem could be 'arcing' that killed a set of the power transistor inside of the laser power supply. How did you connect the laser tube? Can you post pictures of that. How many gallon of water you use to cool the tube?


Marco

[Cflanagan]

Marco, bypassed the ammeter, still not working. I'm using a 5 gallon tank of distiller water, it's not chilled but I run the laser so infrequently that it never has a chance to even get warm. (I check frequently).

The connections to the tube are using alligator clips. Checked all connections, everything is solid.

I've also tested for ground, all appears to be ideal. I did take the cover off the power supply, inspected for burn marks, loose wires, blown fuse, everything looks good.

FYI, the power supply seemed like it may have been opened before, several of the screws on the outer case as well as some of the screws on the main board were mismatched. Almost like it had been taken apart and put back together. Is that possible? Very odd.

Can you help me locate the power resistors so I can test them directly? I can't justify buying yet another power supply until I can figure this out.

If it's possible to send a photo of the power supply board highlighting the power resistors that would be greatly appreciated. Or if there is some other way to identify the power resistors? I'll see if I can test them.

At this point I'm suspecting it's the power supply again. This will be the third one I've had issues with. I'm lost as to where to go from here, I'm getting totally paranoid now that every time I turn on the laser, something is going to blow!

Awaiting your reply.

[Tech_Marco]

Cody:

When you mentioned that you have two power supply die I found it was so odd. When you reported the 2nd one dead, I asked you to try a power supply from other supplier.

Now the 3rd one happened, I'm sorry to tell you that I can't ship you the 4th one but willing to take it back for refund. I don't know what is happening, either our power supply was bad or may be the electricity was not stable in your location. I can't tell so refund seems the best solution.


Marco

[Cflanagan]

Marco,

I've attached a few images that you requested that shows the water system (5 Gallons of Distilled water) Using a mid size aquarium pump that's working perfectly but the water is NOT chilled. As I mentioned before, I only run the laser for a few minutes at a time so i'm pretty sure it's not an issue with the tube overheating.

I've attached another image showing how i've attached the leads to the tube (i'm only showing the Negative connection, the positive connection is the same. Also added a photo of how I have the Power supply connected.

Update:

Today I removed the laser tube from the PVC and inspected it for cracks, etc. Everything looks fine. No signs of arcing, no cracks in the tube and it is perfectly water tight.

I removed the case from the power supply, examined the board closely, front and back, no sign whatsoever of any burnt components, no burnt smell, no cracked wires. From all appearances the power supply is in perfect condition.

I emailed you a video file (125MB so I don't know if it came through) it shows the ammeter "floating" when the tube is not in use. I don't recall that happening before this last problem. It seemed that it was constant at 0.00 MA when the laser was not firing. As you can see in the video, when I fire the laser, the ammeter shows 22.3 MA (Approximately). I have the system set to fire only at 50% power so as to stay within the tolerances of the 60 W tube.

As I mentioned, i'm also using a battery UPS to filter the power, i've tested the ground and it seems solid. (i've been reading tons of forum posts to try and track down any other possible issue).

Lastly, I fired the laser without the ammeter in place, no difference in power. It will barely lase through a piece of paper. I tried firing it through the keypad and also via a switch directly from the power supply. Same result in both cases.

A few questions: Please answer each so I can trouble shoot this:

1. Is it possible for the ammeter to show 22.3ma but still not be firing at full power?
2. If the Power Supply truly is working correctly, does that mean the laser tube is faulty?
3. I can tell that the tube is not nearly as bright as it was before, again, is it the tube or the power supply? How can I know for sure?
4. In a previous post, you mentioned that the power resistors in the power supply could have fried due to arcing. That seems unlikely but i'd like to check that before I send the supply back. If it's simply a matter of replacing a few resistors to fix the problem I could do that myself. I need to know which components on the board you were referring to.
5. If somehow there were a problem with arcing, would that damage the tube as well as the power supply? (again, inspected the tube closely there are ZERO signs of arcing, scorching, etc. It looks perfect.

Marco, just want to be clear, i'm not looking to get something for free, and I certainly don't want to be a problem customer, i really like working with you guys. If i'm causing the problem somehow I'll certainly take responsibility for it, but i've put dozens of hours into this now, i've read hundreds of forum posts looking for problems others have had, i've checked and rechecked every component, and connection. What baffles me is that it was working perfectly, then all of a sudden it just lost power. The last time I had a problem, it was obviously the power supply, as it was fried and I heard it ZAPP! This time, there was no specific event, one minute working fine, the next not.

P.S. The photo of the power supply above shows it set to 220 Volt. That is NOT the problem. I bypassed the switch as was recommended in one forum post to insure the voltage switch was not the problem.

I'm lost.. please help meeeeeee! ; )

[Tech_Marco]

Hey Cody:

Don't get me wrong, I don't mean that you're a trouble maker. I just want to say that I couldn't tell what was the problem. You said that you had tried three new power supply and it worked fine for just a while then got power dropped. It sounds odd. That's why I asked you to try a power supply from other supplier because I really didn't want to send the 4th LPSU.

BTW, I have three questions for you: 1)You seems used "TH" for the "TTL" control. Why was that? Did you set "High level" for the TTL on LaserCad manufacturer parameter setup?

TTL.png (22.66 KiB) Viewed 2330 times

May be that is the cause. I suggest you to connect the White wire to the "TL" (2nd pin from the left instead of the 1st pin), then set the TTL level to "Low level" on LaerCad

2) How did you power the ammeter? Where did you get 5V?
3) How did you connect the Positive of the laser tube. Show me the pictures

I also see that you're using a clip for the negative connection. It is not recommended. Did you do it on the Positive end, too? If so, you're looking for trouble! Remember that the pins on the laser tube is easy to get oxidation. The clipper isn't a good connector because it could get oxidation quick due to the high voltage. You may want to use steel wool to clean the pins and stop using the clipper for connection.

Last question(s): why would you put the tube inside a PVC? How do you know water filled up the tube? How do you to hold the tube firmly?


Marco

[Cflanagan]

Marco,

Yes I was running high level and had set it that way in laser cad. It seemed to work fine. Was getting the voltage from an adjustable wall wart power supply. Used the same power for the red dot laser, it was working just fine the way I had it set up but I can try both hi and low ttl. Though that still wouldn't explain why it would just stop working.

Yes I am using alligator clips on both positive and negative. I was under the impression that's the way it was supposed to be connected. Maybe that's finally the problem? I read that it's a bad idea to solder the connections though. What would you recommend?

I put the tube into pvc and used foam to hold it in place and to protect the tube. It works really well and holds the tube firmly. Since I cut a 12" window in the pic i can see part of the tube and it's obvious the water is flowing plus I can see the beam.

Still need to know about the power transistors. Are you referring to the NPN transistors on the bottom of the power supply board?