I’m wondering if maybe the diode mentioned in the diagram could be relevant? I circled where it mentions a possible blown diode with overload… I found Q5/Q6 so disregard those ?'s, they look good and measure out.
Checking the resistance between the hot and ground? As in, the main output coming from the flyback to the laser? That infamous red wire? Check resistance from there to ground? I’m guessing set the ohm range on my DMM to 20M highest setting?
Warning: this voltage is LETHAL.
Most often connection problems on the high side are easily noticed by arcing.
Letting the LPS arc to ground can damage it as this supply is not designed to operate without a load.
Most often failed culprits in order of frequency:
…Input rectifier bridge
…D70-80
…Q1-4
—
If D90 is bad you can tell by reading the 24vdc on the external connector which will be missing.
Is the green LED on?
Don, firstly thank you for that guidance, I will be closely inspecting the problem areas you mentioned and report back with hopefully some results.
Also, I appreciate the warning about the high voltage. I’ve noticed quite a few K40 owners unaware what kind og voltage the flyback puts out. When the machine was initially shut down, I took precautions, remained aware of my earth, and elevated myself about 14" off the ground by sitting on a plastic milk crate when working close to the flyback. Now the machine has been off for 72+ hours and I’m feeling a little less anxious about a potential charge.
I am now anxious to inspect the areas and components you mentioned, I’ll be back with an update. Thanks again, your technical input is of high value.
Also, one question on the side for future reference… the lack of soldered anode/cathode connections on the factory laser tubes. Is there a reason most tubes are connected with just silicone adhesive? I would like to solder the connections back on the tube, is that not recommended for any specific reasons?
Also Don, just to recap, yes the green LED is illuminated on the PSU when powered on. No damage, cracks, anything unusual on the tube. No power is getting to the tube. I suppose the next big revelation will come when I preform the high voltage “static” test, which will tell me definitively if the problem is in the tube or the PSU. I am taking advantage of the machine being off for 3 days and doing all that I need to do with the machine in it’s current discharged state. Today I will be powering it back up once the tube is back on.
If you supply was working I am guessing you would have already seen arcing or the laser tube light up. I am guessing the supply is dead, not unusual for a K40.
The anode is not soldered at least because heating that pin may damage the tube. I am not even sure that pin is solder-able although I have read about folks doing it? If the wire is properly wound on the pin and then insulated with that white gunk, the connection will be fine. The voltage is in excess of 20KV and connections do not have to be gas tight to work ok. If you were having any connection problems you would see arcs or corona given the supply was working. You can try turning out the lights and see if anything is glowing… sorry but I doubt it :(.
Again, arching the supply to ground may damage it if it is still alive.
I want to thank everyone for your help… I made the decision many months ago to completely quit facebook but one of the drawbacks to that was the info in all the CNC/engineering groups. On the other hand, I ended up finding these google groups that seem to harbor a particular group of makers and engineers whose intellect and experience far surpasses the intellect commonly found on facebook. After all, I do remember reading a study which found that generally, the more successful and happy an individual is, the least likely you are to find them on facebook. I thought about that for quite some time.
Anyhow, I’m at the conclusion that the issue lies within the tube, and I’m going to purchase a new one today, probably from lightobject unless anyone shoots me a better recommendation on sourcing a 40W co2 tube.
We finally had the machine all put back together last night. We took advantage of this downtime to upgrade everything we could, right down to switching out all the janky, loose nuts and bolts with my own SS M4/M5’s w/ washers and thread locker.
Once the machine was powered back up, we went ahead and preformed the infamous “Peanut Test”, in which a Styrofoam packing peanut is tied to a thin cotton thread and suspended in the air. I had the string taped to the kitchen table and carefully maneuvered the laser until the packing peanut was freely hanging in parallel with the HV+ connection to the laser tube. We powered up the laser and sure enough, the high voltage line attracted the peanut and “clung” to the HV wire. I adjusted the trim pot (current regulator) while holding the laser test switch, which resulted in the peanut “dancing” and swaying around, clearly within the field of HV static.
So what this tells me is that the power supply is indeed putting out sufficient voltage all the way up to the laser tube, and even though there are absolutely NO visible signs of damage to the tube, there must be an issue somewhere within that tube that is not visually identifiable.
What do you guys think of this peanut test? This is the first time I’ve actually done it since my grade school science class, except it was more exciting because it was actually a practical test that solved a problem. I think it’s a pretty cool concept, and will maybe help a lot of new users to be able to identify whether the problem exists in the PSU or the CO2 tube.
I took photos along the way and I’m going to do a write up on this whole situation to publish in our blog, in hopes to help others. When I first got a K40, there was ZERO info out there in the internet. Now, there seems to be a decent amount of info but there’s always room for more, and I think this peanut test will be significant and keep people from playing around with flybacks and lethal currents.
In regard to the peanut test. It may tell you that you have a good supply. Then again my reservation would be that it would tell you that there is some static charge but that does not mean that there is an appropriate amount of current or voltage being supplied by the supply. As you know peanuts can show you very small charges like when they cling to your clothes.
I agree we definitely need some safe way to tell if its the tube or the supply when these failures occur without buying expensive test equipment. I have been noodling this for some time.