I bought a prebuilt CyberPower PC and recently upgraded the GPU and power supply. After the upgrade, the computer worked normally for an entire day, although the case fan RGB stopped lighting up. I then added a second 16 GB RAM stick, matching the model of the original as closely as possible. The first time I pressed the power button, the fans spun briefly and then stopped. I realized the RAM was not fully seated, so I unplugged the system and pressed it in until it clicked. I also found and secured a loose GPU power connector.
After that, the PC would not power on at all—no fans, lights, sounds, or other signs of life. I removed the extra RAM and tried the original stick by itself, cleared the CMOS, removed and reinstalled the battery, and tried again, but nothing changed. I used all of the cables that came with the new modular PSU and connected the GPU with the appropriate PCIe power cable.
Could installing the RAM or moving the cables have caused a short or damaged a component? What should I test before taking the system to a repair shop or reinstalling the original parts?
4 Answers
The PSU cables are a major concern. With a modular power supply, every cable must come from that exact PSU; modular cables are not interchangeable, even when the plugs fit. Using cables from the old or another PSU can destroy the motherboard, drives, GPU, or PSU. If all the cables are definitely from the new unit, test with the GPU, drives, and extra accessories disconnected, leaving only the motherboard, CPU, CPU cooler, and one RAM stick.
If there are still no lights or fan movement, try a basic power test outside the case on a nonconductive surface. A misplaced motherboard standoff, loose screw, or pinched wire can short the board. Disconnect AC power, hold the power button for several seconds, inspect for anything touching the back of the board, and then test with the minimum components. If it remains completely dead, the PSU, motherboard, or another component may have been damaged and a repair shop can test them individually.
Double-check the 24-pin motherboard connector and the 8-pin CPU power connector, not just the GPU cable. Also verify that the case power-switch plug is still attached to the correct motherboard pins. You can briefly touch the two power-switch pins with a screwdriver to rule out a faulty or disconnected case button.
Start with the simplest test: disconnect the new RAM and use only the original stick in the motherboard’s recommended single-stick slot, usually A2 (the second slot from the CPU). If it still does not respond, try the other slot and then the new stick by itself. Two sticks usually belong in alternating slots rather than directly beside each other. The first boot after a memory change can take longer while the system trains the RAM, but it should not remain completely lifeless.
All of the modular cables came with the replacement PSU. I did not reuse the old power cables, and I used the PCIe cable for the GPU rather than a CPU power cable. I will recheck the motherboard power connectors and the case-switch wiring.