@donkjr I have a 100W cloudray LPSU that when powered up, always fires the tube, L does not control it anymore, it is “stuck” in always on. Any troubleshooting tips to determine where the fault lies? The only thing working to stop it from firing is the WP circuit, if I break the connection, the laser will turn off.
Can you post a picture of the supply and particularly the circuit card [if that is not a pain] and the connectors.
My guess is the opto-coupler on the input is bad but I do not know if the 100W supply is the same circuitry as the ones I have studied?
I assume that it fires with the connection to L removed.
Ya, fires continuously no matter what the connection, except for the WP circuit which does what is supposed to. I’ll crack open the PSU and take some picks for you. It would be nice to save this one as it is brand new, Cloudray refunded me for it, and it would make a great spare for my big laser.
To start with pictures of the connections and the model # would help.
Is this the supply: https://www.amazon.com/Cloudray-80-100W-Engraver-MYJG-100-Discounts）/dp/B07BBN43SD
If so what does the display say?
Is the P and/or L light next to the connector on?
Is there a wire connected to the H on the supply? L came from your controller but is disconnected right?
It is this one:
With L connected to the PSU from controller, nothing on H, WP enabled, laser fires continuously. Removed L, laser still fires continuously, with nothing but WP connected still fires continuously. Both lights on.
Ok,
With the RED laser light on, as suspected L would seem to be low (ground).
Try these:
- With the supply ON read DC VOLTAGE on pin L and H with a DVM.
- With supply OFF [disconnected from AC] read OHMS to GND on pin L and H with a DVM.
I’ll try and get the tests done tomorrow morning. Thanks for the info Don 
Voltage on L 4.98V
Voltage on H 0.12
Ohms L 7.98ohm
Ohms H 4.2ohm
Voltage on L 4.98V [looks ok]
Voltage on H 0.12 [looks ok]
Ohms L 7.98ohm
[weird, I would expect it to be higher, like open. However how can it read 5V when on if the resistance is that low, that reads like a short?]
Ohms H 4.2ohm
[weird, I would expect it to be higher, like open.]
Does the resistance on H and L read the same if you swap the meter leads.
Hi, going to tag this article here as it might help people diagnose this issue in future.
Sometimes an external pull down resistor can resolve this issue when bridged from H terminal to ground. Not saying this will resolve this issue, but it’s always worth trying. A value in the range of 10k - 15k 1/4w should be sufficient.
Here is an article i wrote about some common failures modes of these power supplies. I am hoping to revisit it in the future and add and amend as needed.
Common failures of a laser power supply
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Very nice write up.
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Thank you very much, we are trying to expand our knowledge base and technical articles as much as possible. If you have any suggestions for new content, feel free to let me know 
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