Question

I you computer powers on with the fans and lights but the monitor be found to have no display, or give messages like 'No signal', 'Cable not connected', 'D-SUB Power Saving Mode' or something similar, then this simply and normally means that the monitor is just not receiving data/signal from the main computer box. The following are possible causes of the computer failing to send signal/data to the monitor as expected. Scroll to the answer sections below for the reset of the steps.

Answer 1

1. Dirty or bad RAM stick - try one RAM stick at the time if you have two installed or borrow one from a friend if you have only one (which you have tried cleaning with no success).
2. System BIOS hang - unplug the computer and press and hold the power button for about 20 seconds and retry
3. Bad GPU - if you have an on-board VGA port and a removable graphics card, remove the card and on-board VGA and observe.
4. A bad PSU - try another power supply
5. A bad CPU - the central processing unit is prone to fail normally due to overheating owing to an inefficient CPU fan on insufficient/dry thermal paste
6. A bad Motherboard - if all else will have be tried by the issue persist, then you motherboard may be sadly bad and due for replacement.