Computer turns on but nothing is Displayed (Black Screen)

[DaylonK]

This computer has been working since 2013, and just lately have I have been having issues.

When turning on the computer, the computer sounds perfectly fine, all fans and everything works. There is no damaged, or burnt anything inside the computer. When turning on the computer my keyboard & mouse do not turn on, and the computer light works and doesn't work. I have tried everything that I can think of and anything that I have researched on the HP guides. And my computer still does not work. I have tried changing monitor, and the cables that connect to these monitors. I have bought a new PowerSupply and that made it work but once I had to restart it it did not turn back on (nothing pops onto the screen, it is black) I went to GeekSquad, and they could not run diagnostics, or run tests on the PC because it was a black screen.

* Note: I have purchased a new Power-Supply, it worked, and then stopped working after a couple of minutes.
- I have tested several different things including:
 1. Testing RAM in different sockets
 2. Testing Monitor
 3. Disconnecting all and any plugs connected to the motherboard (except powersupply-motherboard & CPU)

 4. I have tried changing Power-Supply, (worked for a couple moments and then continued to not work)
 5. I have removed my graphics card, still wouldn't display anything
 6. I have tried exchanging and removing ram.

 7. Tested cords and the connectors.

 8. I have throughly dusted and cleaned all parts inside the computer. (nothing is damaged or burnt)

 9. I have tried running everything normal without majority of things pluged in except: (keyboard mouse)
 10. I have tried to go to a Technician and they told me it is a possiblity that the Power-Supply is what the issue was and that is why it worked for a moment, and then because of a fauly peice in the powersupply it continued to fail. (I am currently getting a new Power-Supply and I will update you below)

Update on PowerSupply: [date] 03/20/2017: (currently nothing here..)

I have a GTX Geforce 750ti FTW graphics card and nothing is damaged or misplaced. All connectors and connecitons work properly. I have reset the computer several times and it still does not work.

Just now when turning on the computer the light (the botton) does not turn on, but the computer does indeed turn on.

I don't understand that if there was something seriously wrong with the computer why it would sometimes work and sometimes not? If the motherboard was bad it wouldn't be working period, let alone working. 

I really need some help, thank you.

[Grzwacz]

Hello

Will try to assist you with this issue.

Unplug any unneeded peripherals. Only use keyboard, mouse and monitor. You could also try different USB ports (front USB 3.0) for keyboard and mouse. You could even try only monitor connected to PC.

Remove all RAM from motherboard. Boot PC and see if you get POST RAM error message. No RAM error message could mean bad motherboard. If you have one stick of RAM try in each RAM slot. If two sticks of RAM, try one stick at a time, in each slot. You could also try new stick of known good RAM in both memory slots on motherboard. 

Then remove 750ti graphics card. Connect monitor to onboard Intel graphics and boot PC.

Unplug HDD's and optical drive from power and try to boot PC with only mouse, keyboard, and onboard Intel graphics. Also try different USB ports and try RAM in different RAM slots on motherboard.

This is a long process to troubleshoot. If none of above helps to find bad component then it is usually a motherboard probem. Could also be a faulty power switch on tower.

Easy fix is take to a PC repair tech for testing.

Grzy

[DaylonK]

I appreicate that you took the time to reply to my post.

All of those things that you have mentioned I have done several times, as explained in my post I went to geek-squad and they couldn't assist me because the screen is black, they cannot run diagnostics or tests. 

For future refrence, I would appreicate if you comment on my posts that you would accurately read my post and give me advice to the best of your ability with the information provided.

[Grzwacz]

Hello DaylonK

You are right. I have wasted your time and my time.

Well, what is left?

Replace the motherboard and/or processor.

Grzy