I replaced my 650W power supply with a 1250W Great Wall unit. The new PSU uses a round IEC-style power connector, and the seller said my existing power cord would be compatible. After installing it, the computer shows no signs of power. The cord is marked 125V, so I'm wondering whether that rating or the installation itself is the problem. I've tried both positions of the rear power switch and don't see a voltage-selector switch. Which cables should I be using, and what should I check first?
3 Answers
The 125V marking on the wall power cord is just its maximum voltage rating; the cord doesn’t regulate voltage. If it powered your old system, it’s probably fine, assuming the plug fits and the cord is in good condition. Check the exact PSU model, confirm the rear switch is on, and make sure the motherboard’s 24-pin and CPU power connectors are fully seated.
Before reinstalling it, you can test the PSU separately using the manufacturer’s approved procedure or a PSU tester. Also double-check that the case power-button connector is attached correctly and that no connector was loosened during the upgrade. If the unit still shows no standby power with its own cables and a known-good wall outlet, it could be defective.
Do not reuse modular cables from the old power supply unless the manufacturer explicitly says they are compatible. The connector may fit while the pinout is different, which can damage components or prevent the system from starting. Use the cables supplied with the new PSU and reconnect everything from scratch, including the motherboard, CPU/EPS, GPU, drives, and front-panel power-switch cable.
The AC wall cord is different from the modular cables that connect to the components. Reusing the former is generally fine if it fits and is properly rated, but the latter should be replaced with the Great Wall cables.
The PSU appears to be a Great Wall 1250W model, and there doesn’t seem to be a separate 120/240V selector. The cable rating alone wouldn’t explain a completely dead system.