HP Z620 turns on and off

[e97]

HP Z620 Workstation will not POST. I get a SOLID BLUE led briefly, fans spin up, and then it powers off. Repeats.

From https://h30434.www3.hp.com/t5/Business-PCs-Workstations-and-Point-of-Sale-Systems/hp-z820-turns-on-a... it sounds like it might a short fault protection.

Verified in other systems:

Processor OK

RAM OK

PSU OK

If I disconnect the 8-pin EPS - the motherboard gives me SOLID BLUE BLINK and then 4 x  RED BLINK => PSU error, so the motherboard seems to be working?

With the 8-pin EPS connected I get the ON / OFF cycle.

If I disconnect the power cord,(only way to turn off system) I get a SOLID BLUE, followed by either 2 or 3 RED BLINKS. This means CPU issue so I reseat the CPU multiple times and even verified it in another system. Also tried a known working CPU.

At this point, I'm thinking of trying the Crisis Recovery Jumper https://h30434.www3.hp.com/t5/Business-PCs-Workstations-and-Point-of-Sale-Systems/Crisis-Recovery-Ju... but don't think it will work since it seems to be a short of some kind and the system wont stay powered on - unless the 8-pin EPS is disconnected. Going to try testing for shorts on the EPS connector..

[e97]

Tried some differential diagnosis..

With only the front half of the EPS connected - 4 pins closest to the front - system stays on and I get 4 RED blinks = > PSU error.

Any time I connect any of the back two +12V, I get the ON / OFF cycle. So I guess the motherboard has a fault somewhere on that rail 😞

Anyone have a trace of the two +12V rails? Hoping its a blown capacitor that can be easily replaced.

[DGroves]

please search this forum for a post from "SDH" on how to recover a corupted bios

based on your description, it appears the bios is corupted and needs to be restored using the factory bios recovery steps

[e97]

With all 8-pin EPS and without the CPU in the socket => No BLUE led and 3 RED blinks.

Looks like a short on the CPU socket.

The BIOS maybe corrupt but I still have to solve the short. I don't see any bent/missing pins - blew it out with compressed air.

[DGroves]

i would try reseating/replacing the existing cpu if The Diagnostic LED blinks red 3 times and the system beeps 3 times (once per second), then a 2-second pause follows:

This indicates that the processor is not installed. or defective or the cpu sockek may have bent pins, or the motherboard is bad

you can get a low spec cpu off ebay quite cheaply

https://static.bhphotovideo.com/lit_files/84998.pdf

[e97]

Verfiied the CPU works in another system.

Cleaned it with compressed air and still same issue.

Here's a picture of the socket. I don't see any bent/damaged pins, maybe another pair of eyes will help.

z620 socket

Probably will try to get a replacement motherboard in the meantime.

[e97 · Accepted solution]

Fixed it!

Was a blown cap causing a short.

Followed the same process described in this video about a short circuit repair on a Macbook Air: https://www.youtube.com/watch?v=hFA4sHIXG8s

[UncleScroodge]

Hello,

Please can you tell where was this capacitor located ?
I have the same on - off problem. The computer will turn on without booting then off then on again endlessly.

Thank you !

[DGroves]

there is no guarantee  that the previous posters bad cap will be in the same location as yours

also you have not said what exactly is happening with your board/boot sequence, please describe what happens EXACTLY when you power on your system

[UncleScroodge]

Yes I know that there is no guarantee that it's the same cap even the same problem.
But it could be a clue.

I press the power button and the computer will try to boot, fan spin for 2 seconds and then it shuts off. Then it turns on again and shuts off the same way. I can loop like this forever. Same as described by OP or here https://forums.servethehome.com/index.php?threads/hp-z620-wont-post-powers-on-and-off-quickly.23300/ .

If I disconnect the 8pin EPS it beeps and flashes red 4 times.
With the 8-pin EPS connected I get the ON / OFF cycle.