HP Z800 shuts down on startup - and randomly

[DGroves]

sounds like a thermal issue related to a part on the board becoming open when the board cools down. and makes contact when hot

get a low wattage hair dryer, and make a nozzle out of cardboard to direct the air flow in a more narrow fashion and then

start heating up the board in one area  in a short burst of air 5/8 sec, then try power on.

do not run the hair dryer for long with the cardboard tube!!!!!!!.. it can get so hot it will catch fire if run to long

5/8 sec  will keep the temps below the cardboards ignition temp

do this untill all of the board has been tested with hot air. you might also want to blow the hot air into the pwr supply intake to see if the issue is on the power supply board

also remove/reseat all of the motherboards power connectors

[titustimuli]

Hi DGroves,

Thanks for your suggestion. I tried many many other options and finalyy resigned to a failure in Power Unit.

They seem to be very rare and pretty much expensive (something like the price of a brand new general publi computer).

For now, the Z800 lies under the desk...

[DWills]

Hi everyone, I'm late to this party , but my Z800 with dual Xeon X5675 and 12x4GB ECC DDR3 (OS Windows 10 professional on Samsung 1tb 850 Pro SSD has seemingly the exact same issue when booting from cold. Starts off with power on and a just as POST begins, turns off. Repeat a couple of times. Finally will get to HP splash screen and then proceed to begin booting, but will shut off again. Repeat a couple of more times and Windows will enter startup diagnostics. From diagnostic screen choose restart. System will restart and almost get to Windows sign in before shut down again. Sometimes will go through next time, sometimes a couple more retries are needed. On reboot I F10 and in BIOS screen to measure system temps. CPU temps rock steady. My conclusion is that until RAM temp gets to 43C and has been there for a while . boot will fail with a complete power off. Consistently. I love my Z800, in every other aspect it's a beast. I used to get random shut offs while doing graphics intensive stuff. I have a GTX 1080 shoehorned in with modified shrouds so it fits. PCI-E power for the GPU was from 2 x Molex to 6 pin adapter and 2 x 6 pin to 8 pin adapter, which seemingly provoded adequate power to the GPU. When system power offs when GPU under load became frustratingly frequent I installed a Booster X5 auxillary power supply in a 5.25 inch drive bay to take the load off the Z800 PSU, GPU load power offs were greatly diminished so I suspected the Z800 PSU is a bit tried and not up to powering my 1080 and the 4 mechanical SATA drives I have in stalled (2x 1tb WD, 1x 2tb WDand 1 x 3tb). But the cold boot issue has me scratching my head thinking maybe power delivery is unreliable until the main PSU has warmed up and it's not just the RAM. It's too much of a mystery to me so I'm thinking of retiring the Z800 and building a new computer soon, which is a pity as the Z800 is a work of art. So currently my only 'solution' is to wait for the system ( RAM and/or PSU) to warm up before successful boot. I'm not about to drop many $$$s on a replacement PSU. I'll just build a new computer. Anyother ideas gratefully recieved, but as this thread is old I doubt anyone will respond. 

[DGroves]

i've seen this before, and it's usually due to a failing power supply or motherboard in fact i've got a z820 board next to me that had the same problems you describe and after swapping out all other parts it was narrowed down to the board in my case once i replaced the motherboard all was fine

you might want to remove all addin cards, drives except for video/boot disk and remove all ram except for one or 3 sticks (depending on module size) to see if less load on the supply changes things, if not then you possibly may have a bad board

[DWills]

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@DGroves wrote:

i've seen this before, and it's usually due to a failing power supply or motherboard in fact i've got a z820 board next to me that had the same problems you describe and after swapping out all other parts it was narrowed down to the board in my case once i replaced the motherboard all was fine

you might want to remove all addin cards, drives except for video/boot disk and remove all ram except for one or 3 sticks (depending on module size) to see if less load on the supply changes things, if not then you possibly may have a bad board

Thanks for your reply. I'm not going to spend any more money on this system. Good Z800 parts are rare and expensive. I'll build a new system as a replacement and gain significant performance enhancement and reliability. In the meantime I'll persevere with the ordeal of cold booting only if I need to. Instead of shutdown and let the system get cold. I will reboot (beboot works every time once warm) then sleep the system.

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[BubbaSawi]

I have couple of Z800, and serviced few of them, and I found the shutting down Issue related to the power supply, I replaced the power supply and the machine start working normally, so I believe one of the power supply components was faulty, I don't have the way to test it, if anyone know how that will help a lot of Us, as the power supply is not cheap.

Cheers 

[DGroves]

Read the Factory Service Manual................... it covers how to enable the power supply self test (BIST) if it passes the self test it's most likely good if it fails then the supply needs replacing

the BIST test checks all rails for proper voltage output