Some notes: @Josh_Hutch be careful… the LPS outputs lethal voltage even if it is not working correctly.
The supply can look like its not working yet has enough voltage while on or if not discharged to be dangerous.
My guess is your stock machine has no interlocks …
Surprising, the supply does not look like its that old.
Not to be an ambulance chaser but if the LPS ends up bad and you do not intend to repair or keep it around, I am collecting dead ones in a continuing attempt to find out why they fail. :).
With symptoms like yours I would guess the HVT in the LPS is bad.
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“…it is chirping next to the HV red cable just not as intensly as it is next to something like the hot black wire in the power cord…”
A chirper will likely indicate anywhere near the LPS as the voltage, even if it is weak, is very high.
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You can measure the voltage at the “IN” pin on the LPS which controls the power level of the LPS. It should vary between 0 and 5VDC when the current pot is rotated.
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You can get parts for your supply from ebay. The exact part depends on what vintage supply you have.
The HV connection to the tube has a HV diode in series with it (in the HVT). Unless it is shorted to ground (not the normal failure mode) it will read “open” but it actually may not be. Reading a high resistance means that it is ok or the HV diodes are open. Not a conclusive test because both good and bad cases read open.
The cathode wire is in series with the meter so I would short out the meter before measuring to prevent any potential damage to it. With the meter shorted it should read 0 ohms to the FG connection on the LPS.
I also noticed on your video that you are not using the earth ground…that is not good as it opens you up to being the best ground depending on conditions. Don has a whole video example on this.
Sounds exactly like what mine did about a year ago. I ended up changing the LPSU & tube, so never got to isolate it to one or the other. There were no visual indications at all it was a bad tube, but I needed an upgraded tube anyways so I just got both the tube and the LPSU.
I found the problem got the repair part in. It was a flyback Transformer. Got her installed, grounded, tested and it works even better than before. Thank you everybody for your input.
Well working with the only tool that I had at the moment I used what was called a chirper. It indicates voltage but it doesn’t say how much voltage or amperage is going through Hotwire.
If it’s a hot wire it’ll chirp like crazy.
If it’s a white neutral wire it’ll chirp a little bit but not quite as much as a hot.
If it’s a ground wire won’t chirp at all.
So obviously it wasn’t really a highly technical device.
What it did tell me though is that the plug into the machine had a very hot wire. The hot wires which are typically black indicated a high-voltage by a very loud chirp and quick beat. The neutral wires still chirped but not as much.
So comparing the sounds from the plug and the hot wires going into the PSU versus the flyback Transformer and the hot wire to the laser itself.
There was quite a bit of difference meaning power was getting into the flyback Transformer but not as much voltage over to the laser while turned on and being tested.
I figured that since the laser would be a high voltage area then the problem should lie between the laser and the flyback Transformer.
Since everything before the flyback Transformer seem to have plenty of voltage but everything after the flyback Transformer had a great reduction in voltage, I figured that it must be the flyback Transformer that was my issue.
After reading other posts and blogs about the laser after and went bad I had no indications that the laser was bad the power supply unit still had green light on and when I pressed the test button on the PSU the test button light came on and I heard a whining sound coming from the flyback Transformer, that was also a good indicator that the flyback Transformer was the issue.
Like I said in a prior response the pump was working the fan was working I knew I didn’t have additional water inside the laser itself.
The other indicator was that I wasn’t getting any results in the ammeter which I’m assuming the power goes through the flyback Transformer and then shows an indication through the ammeter gauge.
So with all that it took my best guess and bought the 40 to 60 watt flyback Transformer version. And the second I plugged it in and got everything wired up it fired up much better than before.
So again thanks everyone for your advice and all the tips to narrow this down hopefully my issue is help somebody in the future and maybe my amateur explanation of how I came to the result that I did may help someone in the future as well.
I have been noodling for some time for a definitive AND SAFE way to tell if the laser or LPS is bad. A test or tester that every K40 user could employ. This is because on these machines these two parts are treated by the manufacturers as consumables.
Creating an arc is the best test I know but its dangerous and inconclusive.
Usually if the LPS will not arc its dead. If it does arc and the tube will not light up its the tube that is dead.
Inductive indicators may or may not work at very high voltages and they generally do not work with DC.
The LPS output is mostly DC so I would not expect much of an indication when bad.
However there is so much energy even on the primary (plus 600v pulsed) you likely would read some activity. Meaning it be a may good indicator, it may not.
Turns out, best I can tell, the guts of the LPS is reasonably robust. When they fail other than the HVT the fuse will blow and its the bridge rectifier.
I think the HVT’s are unreliable because the HV diodes potted inside them are poor quality, potted poorly or perhaps just sized wrong. At these voltages it doesn’t take much to fry a diode.
Removing and testing the HVT may be an option but that would require a fixture that also uses high voltage and perhaps not everyone can build one
I am consumed these days with the OX build but just started to put my K40 back together and continue LPS and PWM testing.
Phew, I was hoping you didn’t get sick and tired of the K40. Your work has helped me, and many others i’m sure, with troubleshooting and understanding the K40. It takes a LOT of patience for this kind of commitment you have with these machines.
@Madyn3D_CNC_LLC not tired of the k40, just lots of family time and learning the nuances of cnc. Learned alot about gcode on mills, tiny G, chillipepr and guess what… found a design problem with pwm control of spindle motors… go figure!