How do you replace a fan on a 550 ti?

To replace a fan on a GTX 550 Ti, first, ensure the GPU is powered off and unplugged from the computer. Remove the heatsink by unscrewing it from the GPU and carefully detaching the old fan from the heatsink and the circuit board. Install the new fan by securing it to the heatsink and reconnecting it to the PCB. Finally, reassemble the heatsink onto the GPU, ensuring proper thermal paste application, and reinsert the GPU into the system.