HP Z440 will not boot - single click diagnostic?

[ericshoe]

My HP Z440 has an odd issue that I cannot seem to find any information on, or anyone with a similar issue...

When I press the power button, the LED on the power button will light up and the fans (processor and system) will come on for approximately one second, then a clicking sound emits from the power supply and everything turns off and repeats every few seconds in a continuous loop. To get it to stop, I have to hold the power button, or remove the power plug which results in the 4 beep diagnostic / red LED for power failure. 

At first I thought it was one of the diagnostic codes, but nothing correlates to this behavior. 

I have tried many of my own diagnostic efforts with no success, such as trying 2 other good power supplies (one being the larger 725w unit), different memory and hardware configurations, and even stripping it down to just the MB with processor and power and still the same behavior. 

Any input or recommendations would be appreciated. I am leaning toward a possible bad MB, processor, or short somewhere, but not sure what else to try without buying parts and trying it out. Thank you-

[Bill_To]

Hi

Sounds like a power supply problem or a system board problem, or a component connected to the MB. The PSU is cycling so you could have a short. Reduce the system to a minimum config to test this hypothesis.

Check diagnostics at this link (http://h10032.www1.hp.com/ctg/Manual/c04823811.pdf )

Look at chapter 4, page 90, Diagnostics and troubleshooting.

[ericshoe]

Thanks Bill - I will review the document further and circle back. I have already tried 2 known good power supplies and also stripped the MB down to a basic config to power the MB / processor only  and the same result. Tried resetting the CMOS as well. Going to pull the MB out and power it outside the case to eliminate the possibility of a short. Thank you. 

[ericshoe]

I just pulled the MB and known good PS out of the case and put them on the floor and powered it on with nothing in it and the same result. I am leaning more toward a bad MB. 

[Bill_To]

Hi.

Yes, I agree.

[ericshoe]

Purchased a used MB from ebay and now all is good! Booted right up. Thank you.