My friend and I are putting together a PC using a mix of new and reused parts. The system works and displays an image when the GeForce RTX 4070 is removed, but once the card is installed, the monitors show no signal and the computer powers itself off after about a minute. The main parts are an MSI PRO Z790-P WiFi motherboard, Intel-compatible 240 mm liquid cooler, 32 GB of DDR5 memory, an MSI MAG A750GL 750W power supply, an RTX 4070 Ventus 3X 12G OC, and an older 1 TB hard drive. What should I check to get the graphics card working?
4 Answers
Do not reuse modular power cables from the old power supply. Modular PSU cables are not interchangeable between brands or models, even if the plugs fit, and using the wrong ones can damage the graphics card or other components. Disconnect the old cables and use only the cables that came with the MSI power supply.
Clear the motherboard’s CMOS and boot with the card installed, then check for any diagnostic LEDs on the motherboard. If the board reports a VGA error, reseat the card and check its power connection again. Once you can get a display, install the current graphics driver; drivers would not normally explain the computer physically powering off before reaching the operating system.
Try a basic hardware check: turn the system off, reseat the graphics card, reconnect its power cable, and inspect the connector for bent or exposed contacts. Test with one monitor and a known-good cable. If the PC still shuts down, remove the card and verify that the system remains stable, then test the card in another compatible system if possible. A shutdown shortly after startup can indicate a power, cabling, short-circuit, or faulty-card issue rather than just a driver problem.
First, make sure the monitor cable is connected to one of the graphics card’s video outputs, not the motherboard. The RTX 4070 also needs its power connector fully seated. Use the dedicated PCIe 5.0/12VHPWR cable supplied with the power supply if applicable, and confirm the card is completely inserted into the motherboard’s top PCIe slot. A 750W unit should generally be enough for a 4070, assuming it is functioning correctly.
The computer displays normally when the card is removed, but I haven’t been sure which output or power cable I should be using with the 4070.
The only parts I intentionally reused were the graphics card and the older hard drive, but I’ll double-check that none of the old PSU cables are still connected.