Are you seeing yellow flashing power button on a Dell PC when you turn it on and nothing to the connected monitor? If so, please try the following to see if you have a power supply or memory issue.
Power Button Status
Blue: Sleep (Optiplex 990, etc)
White: Sleep (Optiplex 9010, etc)
Yellow: RAM/Mobo/PSU (Dimension, Optiplex, etc.)
01. Power off the computer. Hold the power button for 5 seconds if needed.
02. Disconnect the power cable to prevent the PC from restarting.
03. Press the power button twice while the power cord is disconnected.
04. Carefully remove all the RAM (Random Access Memory) sticks.
05. Reconnect the power cord and start the computer.
06. Listen for six beeps from the internal speaker.
07. Power off after the six beeps on a Dell PC.
08. Disconnect the power cable once again.
09. Carefully add one RAM stick to the computer.
10. Reconnect the power cord and start the computer.
11. Watch the front panel of the PC and screen on the monitor
12. Correct any error messages.
If the issue is still the same, the RAM (memory) could be incompatible/defective or the slot on the motherboard. To find out which, you should now power off the computer and switch the RAM to another slot then power it on again. If the computer now works properly after the switch, then you have just confirmed that the slot on the motherboard might be bad or has debris that blocks the pins on the RAM from being detected so make the motherboard vertical can clean with air. To see if your remaining memory is working fine, keep swapping and booting until the last RAM stick. When all RAM sticks are confirmed to be working, you can now then reinstall them all for normal PC operation.
What You Should Know
Manufacturer Dell, as with most companies, provides a limited warranty on their products so expect to find your warranty period between one and three years. Please be aware that the replacement motherboard sent from Dell may be a refurbished one when replaced under warranty.