1. Disconnect the main power. Remove the 4 screws on back cover by knob wrench and remove the back cover.
2. The 24VDC PS is located at lower left corner. Loose the 7 screws and remove the 7 cables. (Take a photo, in case you mess up the connection when recover them)
3. Remove 4 screws on left/right side of the power supply and take it off. Figure 1.4 - 2