Computer won't boot when turned on, then makes a loud fan noise.

[RyanDMiller]

After replacing both my power supply and motherboard due to boot failure and getting the 4 red light beeps every two seconds, the power light is now white with no beeps, but now there's a different problem.

Before, nothing was responding.  Now the fan at least spins, but the computer doesn't boot.  The light is on soon as the computer is plugged in, can't be turned off, there's a black display due to boot failure, then after couple seconds, the fan makes an extremely loud noise that can only be stopped by unplugging the computer.

What's most likely the problem?  Is it the processor?  No thermal paste was reapplied and basically the screws on the side only is keeping the processor in place.  Is this the reason?

Anyone that can help will be greatly appreciated.

Thanks in advance.

Don't forget, I have an HP ProDesk 400 G1 MT.

[Grzwacz]

Greetings,

Welcome back to the forum.

I am not a HP employee.

I would clean the CPU heatsink and CPU heat spreader.

Reapply thermal paste.

Are you saying the heat sink is not correctly installed on the motherboard?

Regards

[RyanDMiller]

Yes, heat sink wasn't reapplied with new thermal paste.  The old thermal paste looks dried out. Could that be the reason?

[Grzwacz]

Hi Ryan,

It's possible.

I clean old stuff on both surfaces and reapply new thermal paste to the CPU heat spreader.

Make sure the heat sink is securely attached to the CPU socket. 

Regards

[RyanDMiller]

Hello. I reapplied the CPU with the thermal paste, but I'm getting the same problem.  It's not booting and makes a loud fan noise.

a) Can this be because all of the old thermal paste wasn't exactly 100% cleaned off? I mean it wasn't even much old paste.

b) If cleaning all of the old thermal paste off STILL doesn't resolve the issue after reapplying the CPU, then what would be the next step to take from here to resolve this issue?  The power supply and motherboard was changed.  Only parts I see left to change are the fans.

[Grzwacz]

Hi Ryan,

You started with a four beep POST error code. 

A four beep error code for your PC can be reviewed at this HP site, page 93 (Link).

This site states a four beep error code may mean the power supply is overloaded. 

Problem resolution suggest to reduce the PC to a minimum configuration. Other possible options are to replace the power supply and/ or MB.

You did this.

Now you get zero POST error codes. It looks like you now have a different problem.

Something is not correctly connected to the MB, the MB or some component may be faulty, or there may be a problem with the new power supply.

You may have purchased a bad component, or may have damaged a component when replacing parts, or have a connection problem somewhere in the system.

Regards

[RyanDMiller]

At this point, maybe I should carry this computer to the shop.

[Grzwacz]

Hi Ryan,

Yes, we can only do so much in a forum.

Regards