My friend and I are building a PC from a mix of new and older parts. The system starts normally and stays on when the RTX 4070 is disconnected, but once the graphics card is installed and powered, the monitors show no signal and the computer shuts itself off after about a minute. The current parts include an MSI PRO Z790-P WiFi motherboard, an Intel-compatible Corsair Nautilus 240 RS liquid cooler, an MSI MAG A750GL 750W modular power supply, 32GB of Corsair DDR5-6000 memory, and an older GeForce RTX 4070 Ventus 3X 12G OC. The only other reused component may be a 1TB Western Digital hard drive. What should I check, especially regarding GPU power cables, monitor connections, and whether the graphics card or power supply is faulty?
3 Answers
A 750W power supply is enough for an RTX 4070, so the wattage itself probably isn’t the issue. Make sure the monitor cable is connected to the graphics card’s ports, not the motherboard. Also reseat the card firmly in the top PCIe slot and confirm that its power connector is fully inserted.
Try starting with the PC powered off, then remove and reinstall the RTX 4070. Check that the card’s power adapter or PCIe cable is connected correctly and isn’t sharply bent near the connector. If the system works normally without the card, test the 4070 in another known-good system if possible, or test another graphics card in this build. That will help determine whether the card, cable, or motherboard slot is the problem.
Be extremely careful with modular PSU cables. Cables from one power supply generally cannot be reused with another, even if the plugs fit, because the pin layouts may differ. Use only the cables that came with the MSI power supply, especially for the graphics card. Incorrect cables can prevent startup or damage components.
The system works normally without the card, but I haven’t been able to test the 4070 in another computer yet. I’ll check the cable and reseat everything before trying that.