Laser PSU dying? I'd like a sanity check on my diagnosis.

[Clinton Crawford]

I've got a 2006-2007 vintage 1200x900 G.Weike machine, and since I bought it, I've been replacing the parts of dubious provenance with parts of better quality. I think the next one is going to be the laser PSU, because it appears to be failing.

I bought it last year, and replaced the (factory!) tube immediately, since it was way down on output. I've been having good luck with the machine until this evening, when I started a job on 1/2" acrylic. Normally I can get it to cut in 3 passes at 80%, 6mm/s. Tonight, I wasn't able to get through it at all.

Double-checked mirrors and optics for alignment, and found no issues. Tube plasma is pink and healthy to my eye.

DSP shows correct power numbers, so I don't think it's weird software ballyhoo between the computer and the machine.

Checked the ammeter, and found it's reading a steady 8mA at 80% power. Normally I would see ~16mA there.

The laser PSU is still the factory unit from 2006-2007, and I suspect I'm seeing its swan song. The machine has maybe 40-60 hours of run time on it since the tube was replaced, and a large part of that has been rastering.

What gets me is that it hasn't gone out entirely, and doesn't appear to be fluctuating in output current. It's holding rock steady at 8mA, which is why I'm doing a sanity check to make sure I'm not missing something silly.

Cheers!

[Wilbur Harris]

Do you have a potentiometer adjustment knob on that thing? Look at everything, software and hardware, that controls power. I can set power limits at least two ways on this Shenhui machine.

[Bill George]

If you have not changed any of the settings either in the software or machine, spend what $200 for the new power supply and be done with it.

[Clinton Crawford]

If you have not changed any of the settings either in the software or machine, spend what $200 for the new power supply and be done with it.

That's the first thing I did, but my friendly neighborhood laser supplier is backordered at the moment, so I'm playing the waiting game until it arrives and I can go pick it up. I'm in the middle of a job right now I need to get knocked out in the next couple of days, and trying to figure out if there are any other possible causes.

Thankfully, I can still get acceptable parts out of the machine, albiet very slowly.


Do you have a potentiometer adjustment knob on that thing? Look at everything, software and hardware, that controls power. I can set power limits at least two ways on this Shenhui machine.

No adjustments that I'm aware of in the machine. current path is HV PS to Tube, tube return to ammeter, ammeter to HV PS. I thought there might be something in software, as I moved to a different computer, but I've cloned all settings in LightBurn, and the DSP is showing the correct power level on its screen. As soon as I can get this job off of the bed, I'm going to take a shot at experimenting with LightBurn on the older computer, and give LaserCAD a shot as well to see if any settings have gone awry.

Additionally, when this 60w tube goes, I'm debating moving up to an 80w tube. My machine should with new tube mounts be able to physically accommodate it. Would it be wise to install an 80W PSU now with my current tube and run it at appropriate current settings for my current tube, or is it wiser to swap like for like now, and do both at the same time when it comes around?

Thanks for the help!

[Jerome Stanek]

Some power supplies have a pot inside them you access through the side.

[Bill George]

Order your power supply from Lightobject dot com, they can ship next day or whatever and give you good advice on upgrading the tube. You need to measure your current tube as not all sellers (ebay/China ) are honest with the "real" wattage of the tubes they sell.

My advice still holds, unless some magic fairy came in and adjusted your PS do not attempt to change.

[Clinton Crawford]

Order your power supply from Lightobject dot com, they can ship next day or whatever and give you good advice on upgrading the tube. You need to measure your current tube as not all sellers (ebay/China ) are honest with the "real" wattage of the tubes they sell.

My advice still holds, unless some magic fairy came in and adjusted your PS do not attempt to change.

Yep! They're my local supplier (Same city, so I can do local pickup). The problem is that they're out of stock on the 60W PSU at the moment, so I'm a bit up the creek.

I'm pretty sure I've got a good tube -- since CO2 laser tube wattage is pretty closely related to physical size, the measurements of my tube match a 60w unit (1200x55). Last week I was also using these same settings and getting correct readings (18mA) and proper cutting power with no problems.


No hard settings have been changed on the laser itself. I'm the only one with physical access to it, and I haven't poked at it. I'm almost done running this job (slowly, in stages. Haven't wanted to risk bumping the stock or altering home position) I'm going to faff about with software and see if that changes anything.

My suspicions are still on the PSU though, given the overall dubious quality of electronics from the factory (no DSP, mismatched stepper drivers, questionable wiring choices, etc.) and the fact that it's still the same one from the factory. It hasn't seen a lot of hours since it was new, but it's still over a decade old, and has been sitting in a dusty shop corner for most of its life before I bought it.

Thanks!

[Bill George]

Well given its how old 15 years or so I would bet on it being bad. But just for the fun of it with the power off, check all the connections with a screwdriver and see if you can find a loose on. Even the HV cable connection can get a little dirty after all those years. Hey its a shot, who knows?

BTW did you ask Marco about the 80W PS?

[Clinton Crawford]

BTW did you ask Marco about the 80W PS?

Emailed asking for an opinion, haven't heard back just yet.

Managed to knock out the job I was working on, so not as much of a rush. Now comes time for a bit more fiddling around to see if there's something obviously wrong.



But just for the fun of it with the power off, check all the connections with a screwdriver and see if you can find a loose on. Even the HV cable connection can get a little dirty after all those years. Hey its a shot, who knows?

I did manage to check one connector, paused the job and unplugged/replugged the connector in the return wire between ammeter and HV PSU. I'm going to hit everything with a dose of contact cleaner and see what happens.

Either way, I think it's about time I replace the PSU, and do some re-wiring for safety. The manufacturer made some questionable connector and wiring choices, which I think I should probably fix before someone has a Bad Day.

[Clinton Crawford]

BTW did you ask Marco about the 80W PS?

Received message back. It looks like there's no downsides with going with the 80W PSU rather than the 60w. I was concerned about operating voltage, as the 80w runs 2kV hotter than the 60w supply, but apparently as long as I keep it below 20mA I should be fine.

I looked at the tube specs for the 60W I have, and it specs 18kV as operating voltage, so I'm still a little leery, but that's probably just my level of understanding.

Thanks!

-C

[Bill George]

Received message back. It looks like there's no downsides with going with the 80W PSU rather than the 60w. I was concerned about operating voltage, as the 80w runs 2kV hotter than the 60w supply, but apparently as long as I keep it below 20mA I should be fine.

I looked at the tube specs for the 60W I have, and it specs 18kV as operating voltage, so I'm still a little leery, but that's probably just my level of understanding.

Thanks!

-C

On HV 2 kV is nothing. I would trust those guys and they sold you the 60 W tube they should know.

[Clinton Crawford]

Haven't ordered the PSU yet, but was running a few light duty jobs which the current lower power works for, and my DSP started acting really strange. I've had a couple of time where it freezes mid-job, and when reset goes into power failure recovery mode, a couple of times where it's randomly swapped languages in the middle of a job (resetting the system resolves this) and multiple freezes/blank screens at the end of a job when I go to start the next one.

This makes me wonder whether or not the power supply is to blame or if the DSP is sending bad values to it. Or if the laser PSU is bad, whether it's causing weird DSP behavior.

Thanks for being a sounding board, it's been helpful with trying to isolate things and figure out where we're at.

Cheers!

[Scott Marquez]

It sounds like you have a challenging problem, maybe you have input power problems.
Are you using a 220volt to 110volt converter? Those have been known for causing problems.
i would suggest checking input power and it’s associated connections.
Scott

[Clinton Crawford]

This machine was built for 110v, and to the best of my knowledge, all components are fine with it.

I'll meter the input and see if anything's changed, but the problem started at random without touching anything. I'm going to attempt disconnecting and reconnecting the DSP to see if there's any cabling issues between the display and the unit.

I might try a factory reset and see what that does as well. I've posted on the LO support forums (I originally bough the DSP from them) to see what they think as well.

Thanks!

[Clinton Crawford]

On HV 2 kV is nothing. I would trust those guys and they sold you the 60 W tube they should know.

Picked up a new 80W supply today, and plugged it in. I think I'm still having some oddball grounding issues though, since with the laser PSU plugged in, the DSP screen still flickers on and off and resets itself, especially on engraving passes.

Also can't seem to get TTL power control to work. I've got it running at 20mA on the ammeter, but that's all it gets. Same power output, same reading on the ammeter whether the power is set to 10%, 20%, 50% or 100%.

Hopefully this is something silly, like a ground path issue. The pinouts on the new psu and the old psu are identical, so I just used the existing chassis harness to plug in.

Cheers!

[Bill George]

Is your HV wire shorting to ground someplace?

[Clinton Crawford]

Is your HV wire shorting to ground someplace?

Not sure what it was, but I spent part of today tearing everything down, giving a good spritz with contact cleaner and putting it back together. All connections are the same, but my gremlins are gone.

Previously, PWM control wasn't working, I was just getting 20mA at all times. Now, I've got properly adjustable power again.

No further DSP issues either. I'm guessing I had a weird connection somehow. Leaks seem to be cured though, so I'm happy.

Thank you very much for all of your suggestions and help! I really appreciate it