Dell Optiplex 780 Diagnostic lights 123, no signal on monitor

[survivalcraftfreak23]

Hi, so I recently decided to get a new case for my Optiplex 780. but then I realized, even know the case is the exact same size, it doesn't fit. so I had to reinstall everything back in the case. However, I've been having troubles with it. for some odd reason, it keeps showing error code 123 on the desktop. I looked at the manual, and it seems like the error shows on the monitor. however, even when i plug it in to the integrated graphics VGA input, it doesn't seem to show up on the monitor. I've checked to see if my monitor was faulty by switching graphics, and it might be. but it could also be the motherboard, too. Could it be that my 2 graphics cards are now faulty?

 

[survivalcraftfreak23]

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