No Display during boot and fan speeding fast

[kochi412]

My Device is HP ProDesk 400 G4 Base Model Microtower PC. After pressing the power button there is no display in it. Fan of the processor is speeding very fast. I have changed the Monitor and RAM, Processor, Processor fan one by one but nothing resolve my problem. How to fix this problem? 

[Bill_To]

Hi @kochi412 

Welcome to the HP Forum.

If I am understanding correctly, you have replaced: the monitor, RAM, and the CPU with no change in symptoms.

Or did you only replace the CPU fan?

Are you getting any startup beep codes or flashing LEDs? A Beep code or flashing LED pattern would be helpful.

The general troubleshooting procedure is to gradually reduce the PC to a minimum configuration until the PC will POST.

Disconnect all unnecessary peripherals. Try only a monitor to check for a POST.

Disconnect storage devices, F_Panel USB and card readers, and any other MB add-ins, one at a time, until you get a POST.

Use: only one stick of known good RAM in each memory slot, one at a time, CPU, and try integrated graphics if the CPU supports this and you have a discrete graphics card.

A no go in a minimum config would suggest a power supply problem, a RAM problem (unless you have access to other, known good, RAM modules to test for a POST), a MB problem, or a CPU problem.

Regards