Dell AIO 7440 having "popping" sound after motherboard change

[hopeng]

Hi, does anyone know what could be the reason for 'popping' sound during windows start (while window icon showing)? I just replaced a broken motherboard and the sound start happening.

Windows starts ok. No noise afterword. But the start up popping sound is scary to me. Not sure if it's safe to use my PC. I've attached the video of the internal of the PC during start up and the sound. thanks.

[mon2]

Re: Dell AIO 7440 having "popping" sound after motherboard change

Sounds like a mechanical knocking sound. Could it be from the fan cooling area? Was that area reworked?

[hopeng]

Re: Dell AIO 7440 having "popping" sound after motherboard change

Sounds like a mechanical knocking sound. Could it be from the fan cooling area? Was that area reworked?

The fan was taken out and restored in order to put the motherboard in. I couldn't see anything wrong in that area though.

The Funny thing is it always “pop” exactly 20 secs after power on.

[mon2]

Re: Dell AIO 7440 having "popping" sound after motherboard change

Is there a possibility of some debris inside the fan blades. The noise may be when this fan kicks on?

We had this scare on an imac thinking that sparks were flying out of the power supply circuit but instead was some tiny particle bouncing around the impellers.

Could the sound be from the speakers? Try to mute the speakers are attach a headset to mute this possibility.