Hi guys, I just put together my Prusa i3 from DIYTechShop (don't buy from them BTW) and on plugging in the power to my PSU something on my RAMPS immediately let out a big puff of the magic blue stuff :'(

I think I might've connected the 12V to the RAMPS backwards... dammit. Anyways I looked around the board and I don't see anything obviously burnt or blackened, couldn't see soot or melty bits anywhere.

So I'm wondering; where should I look first and what components did I likely fry? I read somewhere that the diode D2 will blow if the voltage is put backwards but I'm curious if that's the only thing that would go bad. I just hope I don't have to order a whole new RAMPS and Mega.

D1 and D2 are the most obvious things, but it's possible you may have burnt a track as well.

So I put my ohmmeter to the diodes D2 and D1. D2 read 0 ohms both directions and D1 read 0 in one direction and something like 54MOhm in the other. So I'm guessing D2 is fried (it does have a small ring around the middle that almost looks burnt, as well as a few small dots that look like solder stuck on the side) and D1 is reading normal? Going to try replacing D2 and see what happens, this time with the correct polarity on the power

Diodes are like one-way valves for electricity. Make sure to install it in the correct direction! Match the white band on one end if both parts have them.....