Dell Precision 3640 Tower Service Manual page 56

Steps
1. Insert the PSU into the PSU slot and slide it towards the back of the computer until it clicks into place.
2. Replace the four #6-32x1/4 screws to secure the PSU to the computer.
3. Place the power supply bracket and tighten the two #6-32x1/4 screws to secure the PSU to the computer.
4. Insert the PCIe card holder into the slot on the chassis and press it firmly to secure the holder to the top of the graphics
card.
Next steps
1. Open the PSU hinge.
2. Connect the power supply cables and close the PSU hinge.
3. Install the cover.
4. Follow the procedure in after working inside your computer.
56 Disassembly and reassembly