Project: Too stubborn to admit my mistakes

[Bitter]

So I dun goofed up and bought a HP socket 1150 motherboard a while back, a HP Merlin Rev. A to be exact. It goes along with the 800 G1 SFF computer. The board was super cheap on eBay, only $16 shipped. I first notice things weren't quite normal when I spied that the CPU cooler mounting holes were a little different looking than normal so I snagged a cooler for $8 shipped, then I spotted the non standard power connection to the board and I knew I'd made a mistake. Not being one to give up, and coming to admire SFF computers a bit, I bought a bare bones 800 G1 SFF computer which is only missing the CPU and RAM. I have spare CPU, I have spare RAM, I have spare cases, I have spare power supplies. So here we are, I'm off on an adventure to make this non standard mATX motherboard live in it's new home inside a Dell Dimension 2400 BTX computer case with it's 200W 20 pin PSU (until I hackenstein a different PSU like my 500W 20 pin). Luckily the CPU power connector is a standard and works. I found a spare PCI-e power cable from a dead modular PSU and that plugs right into the motherboard white power connector. The black connector is just a split for providing power to SATA devices off the board and is keyed different than the white connector. With my trusty Fluke 87V by my side down the rabbit hole I go.

 

Checklist of things to accomplish:
Make sure board uses standard mATX mounting - Done!

Hack standard PSU to work with board - To Do.

Hack front panel switch/LED's to work with board - To Do.

Fend off all the flack I'll be getting for this pointless build - To Do.

 

Here's some photos of what I'm up against, pardon the potato quality.

[fargonaz]

Was the case previously used as a bird cage?

[BB TECH]

Looks like the SFF that the mobo came out of had a OEM power supply. Hence the 6 pin there

 

[Bitter]

59 minutes ago, fargonaz said:

Was the case previously used as a bird cage?

No, I think they housed mice in it, the brown wire that (on the dell board) jumped two pins on the switch/led header has gnaw marks. I know the people this computer came from and do some computer work for them from time to time, they're nice people but...there's issues.

 

56 minutes ago, BB TECH said:

Looks like the SFF that the mobo came out of had a OEM power supply. Hence the 6 pin there

 

Correct! The biggest challenge will be to see if I can adapt a 20 pin ATX supply to feed the board. Just getting the board to power on is going to be the hardest thing, I can make some assumptions of what does what based on wire colors and wire gauge. I may be sunk if the motherboard uses some weird turn on for the PSU. Since I have a working system with this same Merlin board I do have a leg up as I can probe it at power on to see what does what.

 

So far tonight I got the power/LED header from the Dell case re-pinned to plug into the HP board with the switch, power LED, and HDD LED in the correct places and that weird shorted wire the OEM boards like to have also in the correct cavity. So with that done now it's onto the harder part which I'll tackle later on, I need to swap a CPU and some RAM into the complete HP system so I can probe and take notes. It looks like two wires are constant at the 6 pin 12V (measured those two with the system plugged to power but off/no cpu/no ram) and one wire at the smaller header with green and white in a single row is 5V. That 5V worries me as those wires go back to the PSU and could be my undoing...except I have some buck/boost circuits and a handful of boost circuits so I can turn that 5V into 12V if that's a PSU turn on or do whatever I need to do voltage wise with it.

 

Irony that the board is a 'Merlin' since it's going to take a 'Wizard' to make this work!

[Bitter]

So yeah some weird stuff turns on the HP PSU from the board, well weird as far as I know. From memory the green wire gets grounded to turn on an ATX PSU, but I never probed that to watch it. Shots are HP Merlin off and then on probed between what seems like ground and green for that HP PSU.

 

I'm going to see what a 20 pin ATX looks like at the turn on wire before it's on, maybe it's similar enough?

[Bitter]

Ok so the green turn on for an ATX PSU is just pulled down to ground to turn the PSU on, we all know this. I need to find out if the board can pull that down to ground and turn on an ATX PSU.

 

Biggest problem so far is that the board gets a constant 12V from the HP PSU on 2 pins of the 6 pin power connector. This is an issue because the ATX PSU does no provide a constant 12V, there is however a constant 5V which I think I can boost up to 12V and power the board when it's off, what I don't know and I'm having a hard time finding is how much power that purple constant 5V can supply. I assume it keeps the BIOS alive and on the HP board also powers up a little green LED so the draw shouldn't be much, not the end of the world if I smoke this PSU. I really am done for the night, I don't feel like soldering at midnight lol.

 

Google never fails to amaze me. Though the PDF link is dead, someone quoted what I needed to know!

EDIT: FWiW, I just looked over the Intel specs (PDF file) for ATX powers supplies. The +5 VDC Standby supply (that is active whenever AC power is connected to the supply) needs to be able to output a minimum of 2.5 Amps and handle surges of 3.5 Amps for up to 3 seconds.

[Bitter]

We have 12V standby power, via boost circuit and 5V ATX standby. Almost there, just need to repin some stuff from the 20 pin to the 6 pin.

[Bitter]

https://www.amazon.com/24-Pin-6-Pin-Power-Adapter-Compaq/dp/B01NAHMULC

 

So no one told me about these. I feel like a bit of a rube now for not thinking to just google this, I guess the good news is that I'm basically doing what this cable does and that the ATX PSU can be turned on by this board. As much fun as this project is...I think I'll just buy the cable and be done with it and know this for the future should I score a cheap 6 pin HP board for building low cost systems.

 

Srsly guys, face palming so hard right now.

[Tristerin]

53 minutes ago, Bitter said:

https://www.amazon.com/24-Pin-6-Pin-Power-Adapter-Compaq/dp/B01NAHMULC

 

So no one told me about these. I feel like a bit of a rube now for not thinking to just google this, I guess the good news is that I'm basically doing what this cable does and that the ATX PSU can be turned on by this board. As much fun as this project is...I think I'll just buy the cable and be done with it and know this for the future should I score a cheap 6 pin HP board for building low cost systems.

 

Srsly guys, face palming so hard right now.

I JUST bought one of those cables today myself, doing an HP Pro 6300 putting a 650w ATX in it - love the old stuff myself as well.  Was going to comment about this cable but...you found it!

[Bitter]

I think I saw it on your thread actually but...didn't want to fess up. I did however google it after seeing it on your parts list so technically I'm not wrong and that's the best kind of right.

 

Still face palming!

[Bitter]

Adapter came, it's kind of wrong. The smaller single row connector to the motherboard isn't pinned right, I need to measure and shuffle some terminals around, but maybe I can get it to work. Currently getting a blink code of 4 which is a PSU issue, I'm determined to make this work or make the magic smoke come out trying to make it work.

[M.J.]

Love it ! It's been awhile ;however, have you solved this ? I'm currently drowning in my own similar project !

Thanks!

 

[Bitter]

Nope, I was pretty sure I fried something on the board then ended up finding the correct albeit proprietary form factor PSU for really cheap and turns out the board does power up and work. Seems like all the adapters I could find listed as compatible for this board come from the same one or two places and are incorrect for this motherboard. So I quit thinking I had let the magic smoke out but in reality I probably just tripped protection on the board and it had to time out or something. Though the old Dell PSU I was testing with wouldn't work either so I may have actually killed something. I was close but the risk of smoking a CPU and RAM which I could for sure use for something else just wasn't worth it to me.