This should help you, and others to find faults in this PSU.

Voltages to expect with three different conditions.

1) PSU with almost no load (2.2k) set to 12V
2) PSU with 1A load (22 Ohm) set to 23V
3) PSU with current limit turned down to about 500mA, from condition (2). Current limit LED is on.

Measurements taken with input GND as reference and not out "-" !