Electronic – How to properly connect Dell DA-2 to PicoPSU

power supply

I'm building a PC with a goal of having it really small and that's why I have a mini-ITX board and a picoPSU (well, not exactly a picoPSU, because it's not an "original" picoPSU, it's a Chinese offbrand (it's much cheaper), this one to be precise, but I don't think that matters). The problem is I can't figure out how to properly connect it to the PSU (or – to be precise – the AC-DC adapter, because picoPSU is just a DC-DC converter and it needs to have a AC-DC adapter). The PSU I have is 220W 12V 18A Dell DA-2 and I've read that it's a quite popular option for different PC-related projects, so there's lot of discussion on it on the Internet, but none of them show how to properly connect it to anything that has only two cables (like the picoPSU I have – I cut the barrel plug) – yellow cable (+12V) and a black one (ground).

I didn't want to cut off the PSU's connector, so instead I plugged it into a 24-pin ATX power extender, cut off the male connector and left the female connector to which I can connect Dell's custom plug (pro tip for anyone looking to do what I'm doing – that Dell's plug does plug in into an ATX power connector and also into an 8-pin GPU power connector, though in the first case there are theoretically two places on the 24-pin connector where you can plug in, practically the best way to plug it in (the way I did it) is to just jam in into the middle 8 pins, because if you plug it into those two places, there won't a clip holding it and the plug falls out and in the second case you'd need to jam it – but it is possible and it does work and you can even plug it out). I was left with 24 cables and because I don't need 16 of them them I just tapped them together, so they don't disturb me.

I have a friend who knows a lot about electrics and electronics and he said that I should just connect (solder) three +12V cables from the PSU and the red cable together and also three ground cables and the black cable together. I also had to connect REMOTE (Signal) pin with ground in order to turn on the PSU, so I soldered it with all ground cables (there were totally 5 cables soldered). So I did that and… it didn't work.

When I plugged it into power, Dell power brick's light turned green (with nothing plugged in the light is orange – the PSU is not powered on). I turned on the computer and it looked like there was a short circuit – computer's power light lit up for half a second (it was more of a blink) and immediately turned off. Also PSU's light had turned off – not even an orange light was shown. I was scared I might had burnt the computer, but I had checked and everything was alright – no components looked damaged. So I tried turning it on again with the same result.

Anyway – I tried different solutions, according to the Internet, my friend and just to my knowledge and here are my observations (all pins are numbered according to this scheme Dell's pinout, where 1, 2, 3 are +12V, 4 is reserved (as far as I know it does nothing), 5, 6, 7 are ground and 8 is REMOTE (Signal):

  1. Pin 1, 2, 3 soldered together with red cable (+12V) from the picoPSU, 5, 6, 7, 8 together with black cable (ground) (it's what I've written above) with the result I've just written.
  2. Pin 1, 2, 3 as above, 5, 6 and black cable together, but 7 and 8 together and with the same result.
  3. Pin 1 and 2 soldered to red cable, 5 and 6 to black, 7 and 8 together as above, same result.
  4. My friend also suggested connecting 4 and 8 – I've tried many possibilities, but none of them worked – the PSU wouldn't turn on and orange light would show up while the computer couldn't be turned on.
  5. The only combination that would "work" is connecting pin 1 to red cable, pin 5 to black cable and 7 and 8 together – the PSU's light would be green and when I turned on the PC it would start normally – I guess, because after about 5 seconds I turned it all off, because I was afraid that only one +12V line would not be enough to fully power the computer for anything more than turning on. Also my friend said that this wouldn't fully work and I guess about 70 watts of power (220W / 3 lines = about 73W of power per line, I think?) is not enough (I've read that similar builds consume about 100W of power)

So my questions are:

  1. Why is there a short circuit (I think that's what it is) when I connect more than one line?
  2. Am I right that connecting just one line would provide a third of all possible power?
  3. How to do it properly?
  4. It just came to my mind – would adding diodes help?

Best Answer

Seems to be a common problem when using the Dell DA-2 with some picoPSU clones:

https://silentpcreview.com/forums/viewtopic.php?p=453665

I had exactly the same problem with my Rgeek 450P and a Dell DA-2, solved it by connecting pins (1,5) to the 450P and pins (2,6) directly to the CPU. By doing this you can use up to 2/3 of the 220w

  1. If you connect all three lines to the picoPSU, as far as I know every 12v picoPSU would be passing 12v directly to the CPU anyway, so you shouldn't have any problem by doing it like I said.
  2. You will have no more than ~70w on each line so before doing it, find your CPU TDP and estimate how many watts your motherboard, components and peripherals would be drawing from the picoPSU. Also, disconnect your hard drive (You don't want to loose your data in case something goes wrong) and others peripherals until you know everything works fine even under high loads.

That being said, do it at your own risk only.

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