My Aquabot Turbo is 7 or 8 years old.

I am having a problem with the power supply. When I flip the rocker switch to the "on" position, then push the black reset button, the rocker switch lights up red as it is supposed to, but then immediately goes off. Sometimes it will stay on for a minute, but it does not stay on for longer than that. The same thing happens if I try it without the robot attached to the power supply, so I know the problem lies with the power supply, not the robot itself.

Any ideas as to what is wrong with it?