Mean Well PSU issues
I want to use an externally-mounted Mean Well LRS-350-24 in order to keep it outside a hot enclosure. The original PSU is still functional and in its original position on the printer. Disconnecting the power cables from the original PSU and connecting them to the Mean Well PSU gives 24V as expected at the power connections on the Buddy board. The printer turns on without issue, and things seem to be in working order except when the heaters should turn on. They don't. Instead, the printer reboots and gives an error (23201 or 23202 depending on what heater failed to heat up). Thermometers show no temperature increase at all, and the bed power LED stays off. Returning the power connections to the original PSU returns proper heater functions.
What might the cause of this behavior be, and how can it be fixed?
RE: Mean Well PSU issues
Unless you can describe exactly how and where you are connecting to the Meanwell, any wires you are adding, or not adding (Power Panic?), etc. It's probably as simple as you're connecting to the wrong lugs on the Meanwell. But difficult to say. Post some photos of the connections and wires on the Prusa supply and then how you have them connected on the Meanwell.
RE: Mean Well PSU issues
"exactly how and where you are connecting to the Meanwell," The two doubled power cables as on the original PSU, and a ground wire from the Mean Well's ground lug to the ground lug on the original power supply (which is still connected to the Buddy board and display). The power panic cable is still plugged into the original power supply. I did not notice any difference in behavior with having it connected (with the old PSU off, or on with the power cables disconnected), or disconnected, so I didn't mention it. Considering that the printer didn't go into power panic, and that it lives plugged into an oversized UPS, it doesn't seem relevant.
"It's probably as simple as you're connecting to the wrong lugs on the Meanwell." As I mentioned in the original post, the new power supply delivers the proper voltage in the proper places on the Buddy board. That is, I checked that the connections are not reversed. It supplies power in the same polarity as the original PSU did. The printer powers on and can run the steppers with the new PSU. What do you think photos of the connections would show?
RE: Mean Well PSU issues
Photos of the 'failing' setup would be instrumental if offering an opinion. Having the grounds in series as you've describe is prone to having problems, as is leaving the PP feature connected to the unpowered original supply or worse, a powered unused supply. I also suspect you may have added wire to the original bed and nozzle heater cables so you can move it outboard the enclosure. All of these may explain the problems you are having.
Anything less than actually seeing what you have made leads to guesswork. For example, maybe you have a a couple of feet of 22 gauge wire from the new supply to the original lugs. I could guess that's what you have done and say the power supply is insufficient due to the added wire and termination resistance.
The failures you are describing what would happen in my guess scenario. Did you use an oscilloscope to monitor the transient DC voltages at the buddy board while the fails are happening? Do you know the voltage is actually remains at 24v for the crucial few milliseconds the printer decides there is a heating problem? A simple voltmeter can't measure this.
A photo is, as they say, worth a thousand words. I could bore you with a thousand questions - which I won't, or you can take a couple photos. By the way, I am using that exact supply on my Mk3, and it works very well.