Computer flashing on and off

[Corey]

Hey guys, hate to bother you with more problems, but my dad just got his computer back from a repair shop and it's been doing this weird flashing thing since he got it back.

He sent it in because it had a virus or something, I forgot, but they had it there for like a month and just sent it back to him supposedly working now. Well apparently not.

It only happens if you open the cd tray, which is obviously a problem for him since it's the only thing he uses it for. I was thinking it may be bad placement if the power supply cord or something, but I'm not really savvy to what goes on in a computer so I was hoping someone here had an idea. I was hoping I wouldn't need to crack open the case if it was a software problem, and I don't want him spending another 300 bucks to get his computer back worse than it was before again.

Sorry if I missed any typos in this post, I'm typing on his tablet.

[deadlegion]

Desktop or laptop?
Do you mean it is rebooting or just the screen is flashing on and off?

[Corey]

It's a desktop. It's the screen flashing on and off. I thought it was similar to my PC that has a power supply set aside to keep it running for a minute if power goes out.

[MaslowK]

Just a shot in the dark but are you running your video to your monitor via HDMI (one of these)? That type has issues where certain actions cause the video signal to flash off then back on. It could also be a very specific driver issue between your CD-ROM and video drivers. If the computer has a brand name or model number (or sometimes a service tag) somewhere on the case, you should be able to find a support page for the manufacturer and the appropriate drivers.

On the other hand, if your monitor is actually losing power during the flashes, then the only thing I can think of would be that you're drawing too much power on whatever circuit the computer and monitor are plugged into. You can try powering one or the other on a separate outlet and see if that changes anything.

[deadlegion]

Why did it go to the repair shop originally? Did they have any reason to open the case?
Sometimes such shops (dodgy ones, or they just have untrustworthy employees) can swap out parts for other used parts. A faulty PSU can sometimes cause intermittent power issues with various components. But if the monitor isn't piggybacked off the PSU I'm not sure if this is possible I guess if the video card isn't getting the right amount of power?

If I was there myself I'd attempt to isolate the issue through a process of elimination, but I'm pretty crap at guessing what the problem could be.

[IndorilNerevar]

have you checked the psu cable behind the cpu? maybe the psu cable are getting overloaded making the monitor go and off. if the cable is somewhat smoked and the wires are beginning to show. you better replace the cable with a new one or you can try plugging the monitor and the computer into another power socket.