I've run into an issue with an old PC that was working fine before.
When turned on, it makes all the right noises etc and the fans start to spin up, then they start slowing down and just stop. Nothing appears on the screen, it just says "No signal".
I'm 99% sure it's something to do with the graphics card - I had tried adjusting it to make sure it was sitting right and then it suddenly booted fine, but then started turning off again after I rebooted. Makes me think the rest of the PC is fine cause that was the only thing I'd touched. I can't really tell if there's a problem with the contacts on the card or the PCI-E slot or something though.
If I unplug the DVI from the card the screen wakes up and changes to "Cable not connected", so I guess it is still detecting the card. When I boot the PC the GPU fan doesn't spin, but when I hold the power button for 5 seconds to kill it, it briefly spins right as everything turns off.
I can't even get into BIOS or anything because the screen doesn't come on.
Motherboard is an HP M2N68-LA, GPU is a AriesATX-21-M04 (both came with the PC, it's an HP prebuild).
41 Answer
This is a power problem of some kind. And it may involve the graphics card but the easiest things to check don't.
First, disconnect every USB and firewire device from your computer. Yes, including mice, keyboards, hubs, wireless adapters. If anything is plugged into a USB port unplug it from that port. This also means disconnecting any internal USB devices you might have connected to the motherboard headers (flash card readers, etc). Then disconnect power from the computer and walk away for 5 minutes or so. When you come back restore power but don't plug any of the usb devices in. Try to start the computer. If it works then one of your usb devices are shorted out.
If that doesn't work, remove power from the computer again and then disconnect all power connections from the PSU. Then remove all expansion cards and the memory modules (but not the CPU). Unplug all SATA connectors as well. Then carefully reconnect/install each removed component, taking your time, and being sure they are all seated completely in their slots/plugs. Then reconnect the PSU the same way. This will ensure none of your components are failing to make a clean connection to the mobo or the PSU. It will also eliminate the possibility of a component half-in-half-out of a slot shorting out multiple contacts in the slot.
Failing that, you're probably looking at a defective or incompatible component. If your motherboard has onboard video start by removing the GPU and trying to start the system without it. If that works it's either the GPU or the PSU doesn't have enough power to also run the GPU or the PSU's rail that provides power for the PCIe connectors is failing. It could literally be any component in the computer but the single most likely culprit with these symptoms is actually the PSU.
From there I would test components by temporarily replacing them in this order (order selected based on ease, likely availability of spare parts to test with, and the likelihood of it being the cause of the problem).
- Optical/HDD/SSD drives (just disconnect them)
- PSU
- GPU (if you didn't have onboard to test with)
- RAM
- CPU
- Motherboard (which likely means new RAM and CPU too since it's an old system)
Or take it to a technician.
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