RAMPS 1.4 Won't Power On with 12V PSU

Hi guys I'm super new to the world of 3D printing.

I purchased a RAMPS 1.4 Board kit with MEGA. Anyways I got everything wired right but for some reason as soon as I plug in the green 5A 12V power clip(I'm not using the 10A as it's on a external MOSFET) The power supply shuts off and nothing on RAMPS works. I took all the wiring off and stripped it down to just the RAMPS board and the MEGA and plugged it in and still nothing. The power supplies green light shuts off. So then I thought let's try turning the power supply on without the green connector connected to the board. I did that and the power supply works. I'm getting a 12V reading on the PSU as it's brand new, when I plug a external 12V power adoater or the USB into MEGA, the mega works just fine and the RAMPS board flashes its lights. Maybe I'm suspecting the RAMPS board is no good? I mean it's pretty impossible to wire incorrectly with just two wires running from the PSU to the + and - on the green clip going to RAMPS. Any thoughts?

Look under the ramps near the plugs for any solder blobs that shouldn't be there

Yeah I tried that, let me see if I can get a picture for you guys. Oh and thanks soo much for taking time out of your day to help with this! I appreciate it!

Edited 1 time(s). Last edit at 03/22/2018 09:39PM by Fiyero88.

Looks ok

Are you 100% sure you wired it correctly, Gnd on the outermost pin and 12v on the next pin In,

ie




Got anything useful like a multi meter?

What the resistance from +12 to gnd on the 5amp plug? on the ramps while its all unplugged

I'm wondering if D2 (reverse polarity protection diode) is shorted, the diode just behind the fuse.

Another remote possibility Ive seen, check the numbers on the mosfet, ie that they really are mosfets... seen at lease one where the supplier shipped it with 7805 voltage regulators

Edited 1 time(s). Last edit at 03/22/2018 11:13PM by Dust.

Yeah I'm thinking it's the D2 that would make most sense, it's a brand new board but ya know the Chinese things are cheap and no QC.