Z820 shutdown issue

[ducter51]

Suddenly my HP Z820 workstation won't boot. 4 bleeps (with rere panel red LED flashing) & then shutdown. I suspected the PSU had gone faulty. I exchanged it for a replacement, but fault condition remains. I disconnected all add ons (graphic card DVD unit IDE expansion card etc) but no luck. I removed all the memory modules & the 2 CPUs, but the beast keeps emitting 4 bleeps & then switches off! I'm probably looking at a duff MB? But I suspect it could be a problem with the memory. Like if I put everything back together again, and leave the memory out would the PC bleep 4 times?  I have looked at all the possible senarios (getting 4 bleeps) but the information is mostly PSU or MB related. I think I can rule out the PSU. I'm reluctant to replace the MB, when it might be some other smaller issue. Any help would be welcome. It appears to me that the high construction quality of it's electronics would suggest that it's a tough bird?  

[DGroves]

READ THE z820 SERVICE MANUAL............................(posted on the HP site)

it covers how to do a power supply "BIST" test and covers all the error codes

4 beeps/lights indicates a power related issue, either the power supply itself or a addin card or motherboard

https://support.hp.com/us-en/product/troubleshooting/hp-z820-workstation/5225041

also a REMINDER, using the forums SEARCH FEATURE BEFORE POSTING will show previous posts/replys

https://h30434.www3.hp.com/t5/Business-PCs-Workstations-and-Point-of-Sale-Systems/z820-no-power/td-p...

[ducter51]

Thanks for your reply DG.

Yes I had previously viewed the HP website on the link you supplied, and followed the advised checks as  posted there.

Unfortunately none of that related info provided a cure! Now I have almost dismantled the entire PC in an effort to find the trouble.  For a moment I did notice on the main power connector to the MB that the cable insulation had perished (with the

sharp bend applied to it) exposing split sections of bare wiring. But on removing the RH panel and checking I could not establish a short circut on this cable loom to the chassis  While I was here (with the panel removed) I had the opportunity to

check all wiring looms, and ring them out with my multimeter.  All checked fine here.  Now i  went back to the2 CPU's and

outed them again.  On very close inspection (using an old projector lens) I have spotted, what appears to be pit marks on

both processor pad connections.Only 2-3 pits (on both  chips) but seriously looking non- the- less.  I'm unable to verify if this has spread onto the pin connections of the CPU scokets?  Looks to me if some of the heat sink paste had found it's way into the socket pin(s) on the MB.. I wonder if this is my problem?  Iv'e stopped for a rethink about everything, and looking like I will have to replace the MB + the 2 CPU's.   Only have the PC a few months. It was an Ebay purchase. It was working great until disaster struck !     

[DGroves]

discoloration on high wattage (130/150 watt) cpu pads is normal

insulation missing from the main MB power harness is not! you may have had a momentary short in the harness which has damaged parts

as it's hard to source just the wiring harness either look for a bare bones z820, they can be found rather cheap on ebay or better yet jump up to a z840 if you can afford it

[ducter51]

So after a search on Ebay I have tracked down a new MB, and it's main  power cable harness,  I believe I had a number of faults that caused the death of the MB. The 1st was the signs of arcing on a few of the connecting pads of the 2 cpus, and  their related MB socket pins.  The second was the splitting of the insulation on the main power harness, that likely caused a short circuit to add further destruction!  I had been upgrading my workspace, and was moving the Z820 around a fair amount, so this somewhat shifting and moving  (carefully mind) may have brought these hidden problems to the surface?  I hope my CPUs, memory, and GPU have escaped harm?. Hope to be up and running again soon. Thanks DG for your input.