At the risk of stating the obvious... but it sounds like you may be new to this, so **please be careful**!
Half of that power supply is connected to the mains and will possibly hold enough charge to be dangerous for several minutes after it's been unplugged. Charge will be stored in the big cylindrical black capacitor on the lower-right of your photo. After unplugging the board, and before handling it, measure between the leads of this with a meter set for DC volts, and check that there is no more than about 20V present.
Good luck with the repair!