Instead of digging further into the circuity, I decided a little sanity check was needed. Output current and voltage data were taken trying to better characterize the issue being seen. I borrowed a bunch of 50W, 1% resistors and took readings. The power supplies were set at 12V, 5V, and 3.3V. (see the spreadsheet below) The short circuit current is still folding back to the 30mA to 50mA range.
I looked at another physically similar power supply, a 15 year old Mastech HY3003 (single output, 30V, 3A). When the output is shorted with the fluke meter, the current draw goes to 2.07A. (tested at 12V, 5V, and 3.3V)
A BK Precession 1735 power supply (single output, 30V, 3A) was also quickly evaluated. When the output is shorted with the fluke meter, the current draw goes to 3.36A. (also tested at 12V, 5V, and 3.3V)
Amspire, I think you’re right there might be some type of foldback current limiting on a direct short of the MPJA supplies. It might be to keep the power supply from overheating? I did set one of the power supplies to 29V, with a 10 ohm resistor, the current draw was 2.86A.
So, maybe the MPJA power supplies are functioning as intended?