I have the Z400 for the last 4 years. Have been working great.
Couple of weeks ago, one of the hard disks connected to the system was faulty. I opened up the chasis to remove the faulty hard disks. When I put everything back, the workstation went into the 4 short beeps (4 red LED flashes for me as the front speaker is not working). I have followed the diagnosis on page 196 of this guide to determine the problem:
http://h20628.www2.hp.com/km-ext/kmcsdirect/emr_na-c02589908-1.pdf
At first I thought it was the psu since the psu fan was not spinning. I managed to buy a good refurbished psu and connect it to the setup. Same prblem- 4 short beeps. I went through the steps again, even removing the cmos button battery for over a day (to erase its memory). Same problem persists.
I am now suspecting the motherboard may be compromised. Before I embark on searching for a replacement (which may be a challenge, considering the age of the workstation), is there anything else I should try??
Thanks.