EliteDesk 800 G4 Power button not working after system changes

[Fishinforfacts]

I have a HP Elitedesk 800  G3 SFF  that had a bad motherboard so I decided to just do a system upgrade by purchasing a motherboard for an Elitedesk 800 G4 SFF to replace the G3 motherboard with.  I have the I5 7500 processor with 16G ram. I updated the ram from 2400 to 2666 Mhz as well.  When I try to power up the upgraded PC I get no flashing lights and no beeps. I get a momentary white led near the power switch and occasionally a momentary white power symbol on the power switch and the fan runs.  It is just momentary though.  It will not stay running. To resolve the problem I have changed the CMOS battery, removed the CMOS battery and held down the CMOS reset button for 30 seconds and then  put the CMOS battery back in and plugged it back in, and unplugged the PC held the Power button for 15 seconds and the plugged it back in while continuing to hold the power button. None of these things have helped.  Would it benefit me to go back to the slower memory since to my knowledge the faster memory is not supported by the I5-7500? Is it a situation where the G4 motherboard will not support the i5- 7500 and I need to go to an I5-8500? Has anyone got any other suggestions as to the problem or resolution?

[BeemerBiker]

This sounds like a serious problem and not just the on / off switch.

When a system turns off immediately after being turned on usually something is not connected correctly.  Modern supplies detect a short and instantly shut off.

I would unplug all sata devices, fans from motherboard, pull all cards including graphics card (assuming on board video exists) etc.

Some 3 and 4 pin motherboard connectors looks exactly like a fan connector but are not.  Make sure graphic card (if required) is seated properly and power cables are attached.   Look at your power supply for a set of cables that seem to be "left over" 

HTH.

[Fishinforfacts]

Thanks for the reply. I double checked all the power supply cords by unplugging and re-plugging to no avail. I don't have any SATA devices other than the DVD drive so also unplugged it. I changed out the 2666 Mhz memory and put the 2400Mhz in. I removed my SSD. I removed the option board. None of these things had any effect. Next I decided to replace the I5-7500 CPU with an I5-6500 CPU that I had. Eureka, the computer powers up and the fan stays running. The bad news is that the display ports don't seem to work as nothing comes on the display. An ethernet cable plugged into the ethernet port causes the lights on the ethernet port to light correctly. Also, when I try to power down using the poser button, it generates an error code and beeps with 3 long red followed by 4 short white which means  "The system board displays a power failure (crowbar)". So there was some progress, but still not working. The power supply is new. This leads me to believe the problem is with the motherboard. Thoughts?

[BeemerBiker]

There is a big difference in the two CPUs and it is NOT the speed:  The graphics processor,  CPU series and memory speeds are different.  I suspect the bios needs to be updated.  I went and looked a the bios file (it is huge) and pulled out the history.  HP made 16 changes to the bios of your system and unfortunately, there is a warning that earlier bios cannot be restored if a new one is put in.  That warning leads me to suspect that one of the former DEC software engineers must have designed the bios.

---

C:\temp>find "Version" history.txt

---------- HISTORY.TXT
Version 2.16.00
Version 2.15.00
Version 2.14.01
Version 2.12.00
Version 2.11.01
Version 2.10.00
Version 2.09.01
Version 2.08.00
Version 2.07.01
Version 2.06.03
Version 2.04.01 - Fixes issue where system would when resuming from sleep with TBT External Graphic card attached.
Version 2.02.04 - Update ME to 12.0.7.1122 for Intel Quarterly Security Release.
Version 2.02.00 - Add Event logs in F10 BIOS menu.
Version 2.01.09 - Security update with new MCU version.
Version 2.01.08 - Initial BIOS release.

---

It is difficult to update the bios on a system where the display is not functioning. I have done that before but it was a PITA.

I also noticed that the bios file includes both graphic "vbios" as well as motherboard bios.

[Fishinforfacts]

I don't even know where to begin with this if I can't see the screen. Thanks. Since this is the motherboard for a g4 I might be best served to buy an I-8500 since that was the processor for the G4.  It would have been cheaper to have bought a G4 than all the pieces. I had researched and read that you could use an earlier generation I5 in a newer mother board.  The response was not specific to HP.

[Prométhée · Accepted solution]

Hi

you say you bought a motherboard of another model, the HP EliteDesk 800 G4 Small Form Factor PC, is that right?
did you check the compatibility simply

https://support.hp.com/us-en/product/hp-elitedesk-800-g4-small-form-factor-pc/21353718/document/c060...

Intel Core i7-8700 processor

Intel Core i7-8700K processor (95 W model only)

Intel Core i7+ 8700K processor

Intel Core i5-8600K processor (95 W model only)

Intel Core i5+ 8600K processor

etc

Maximum: 64 GB

Number of slots: (4) DIMM

Up to 2666 MT/s

"I went and looked a the bios file (it is huge) and pulled out the history. "

https://support.hp.com/us-en/drivers/selfservice/hp-elitedesk-800-g4-small-form-factor-pc/21353718

Associated files

Associated files accompany the above software file

HP recommends downloading and reviewing README/Release Notes files before installing drivers, software and firmware.

Release Notes

Download

[Fishinforfacts]

I put in my original post that I was updating from a g3 to a g4.  The g3 supports the I5-6500 and the I5-7500. It g4 supports the I5-8500 but I found an answer, not specific to Hp that you could use an older processor in a newer board. Apparently that's not the case with HP. I know that their compatability list does not show the older processors but I interpreted that to be the configurations they sold with the G4, not including that earlier processors would not work.

[Prométhée]

nothing is less certain than the uncertain
This might work in some cases, but motherboards are hp specific
the tdp, and socket are except error the same, but that is not enough
your problem may not be there, but it is a possibility
The motherboard is new, not a used one?

HP EliteDesk 800 G3

Intel Q270

https://ark.intel.com/content/www/us/en/ark/products/97123/intel-core-i57500-processor-6m-cache-up-t...

Find boards compatible with the Intel® Core™ i5-7500 Processor in the Intel Desktop Compatibility Tool

intel® 200 Series Desktop Chipsets

HP EliteDesk 800 G4

 Intel Q370 PCH-H—vPro

https://ark.intel.com/content/www/us/en/ark/products/129939/intel-core-i58500-processor-9m-cache-up-...

Find boards compatible with the Intel® Core™ i5-8500 Processor in the Intel Desktop Compatibility Tool

intel® 300 Series Desktop Chipsets