Adjustable DC regulated supply current is unstable
Voltage regulator type is different, the circuit is also different, a wide range of regulated DC power supply (output for a start to a high specific value) it works is to first stabilize a high voltage such as 18V after a voltage regulator circuit, In the maintenance of the eyes with a multimeter but also to measure the voltage of the previous level, such as 18V are not stable, followed by the adjustment of the voltage is in front of things
This seems to be a component performance instability. Capacitors, diodes, transistors are possible.
Your question did not make it clear that the load is the case of the current instability or how the matter.
DC power supply is stable voltage, the current changes with the load changes, such as the load is the audio equipment, then the volume is large, the greater the current, so the current instability is normal.
