HELP! - First build Pre-Flight test CRASH

So im In the middle of my first build - a Prusa i3 with Ramps 1.4, these drivers: [www.pololu.com], and a 750W Corsair PSU
I just did a preflight test of the elctronics that ended in disaster.

I uploaded this code:
[reprap.org]

I attached 1 Stepper motor and driver to the slot normally used for a second extruder (cant think of a reason why that would be a problem)
Attached 3 endstops

Plugged in my PSU (tested unplugged - no shorts, 12V on each power rail)

Turned on my PSU - at first nothing.....LEDS dont light, nothing happens. Then after 5 or so seconds: BANG! the sound of a spark that scared the shit out of me and the smell of electricity gone bad. I hurriedly unplugged everything and surveyed the damage...but I cant find any! The arduino appears to still work. Powers up on USB and my computer sees it. LEDS are blinking away.
Cant find any sign of damage on the RAMPS board or the driver (the driver has a heatsink glued to it though)
I started to smell around for burned electronics, but after 20 or so seconds after the spark the smell is gone. Can't find it and as I remember from previously ruining electronics that tends to linger doesnt it?

I'm afraid to plug anything back in. any advice on how to proceed safely?

just because I feel like this will be asked: I did not solder my own RAMPS board. I bought it from Amazon from a seller with a great reputation. I inspected the board when I got it comparing it to pictures and all looks fine.

Edited 3 time(s). Last edit at 10/21/2013 02:16AM by McSquid.

I would suggest a fire extinguisher if you don't already have one. I would think trying it again might work, but I would check to see what others say first.

Ok I did some further poking and i noticed I cannot turn the arduino on with a battery. then I smelled what I think is the 5v regulator (next to the barrel jack) and it does in fact smell dead. So I think I have found the source of the problem. Not sure what to blame in this situation but since the arduino still works on 5v I suppose ill count myself lucky. Does anyone have any idea why this would happen? The Arduino does NOT work off USB if the RAMPS board is connected to it.

EDIT: More poking around reveals that the RAMPS pins that normally connect to the arduino 5v and GND are shorted somehow. Cant seem to find the short but this has to be the problem

Edited 1 time(s). Last edit at 10/21/2013 04:14AM by McSquid.

I had a very similar thing happen to me.

I'd connected 1 or 2 of the motors and was doing some basic tests, I noticed the fan on the 12V PSU come on even though all the motors etc were off, and after about 10 seconds I had a Bang, some sparks and smoke, came out from under the RAMPS, roughly where the power pins are on the Arduino.

After some investigation I realised that the Arduino was fried, most of the supply appeared to have shorted together.

I removed the voltage regulator from the Arduino (unsoldered), but was still no good, everything appeared to be shorted.

Fortunately I had another Arduino Mega 2560, which I bought for a different project, but before I connected it to the RAMPS, I cut the track on the RAMPS that feeds 12V into the Arduino, so that it would be impossible for the 12V PSU to drive a large current into the Arduino and destroy it again.

Things seemed to work a bit with the new Arduino, but all the stepper drivers had been blown up. :-(

So in the end I decided to replace the RAMPS and buy a new board + 5 stepper drivers.

On the new RAMPS I also cut the PCB track to prevent the same thing happening again.

I still don't know what really happened.

One easy (and embarasing) way to get this sort of thing to happen:

Wire the power connector on the Ramps as +,+, -,- rather than +,-,+,-. Another way to do it is to get the -12 V supply onto one of the Ramps inputs.

If you pull off the stepper modules, there is not much on the Ramps other than capacitors. If it still acts shorted, you may have blown a cap. It's possible the cap was in the board backwards. It's also possible that it simply was defective. Blown electrolytic caps usualy aren't subtle. They throw crud all over the place when they go. Blown ceramic caps are rare.

Problem is sorted out. It was a bad quality/defective board. solder blobs were under black plastic on the pins shorting them out. I got a replacement from the seller that is WAY higher quality. He said they switched suppliers on those boards and it shows.

By the way if anyone lives in the US and needs an awesome supplier who will go above and beyond for you: Folger Tech (https://www.facebook.com/FolgerTech) (sindewinderinc on ebay and amazon) Is amazing. My J head was delayed due to issues with the nozzle availability so he included a full set of bearings in the box. I casually asked if he sold thermistors because my bed came from china without one and he sent me one for free (actually my new ramps ended up in that box by pure timing chance) He also ships things very quickly. usually get my packages in only 2 days

Thanks for the heads up on the vendor.

Quote
rogerclark
On the new RAMPS I also cut the PCB track to prevent the same thing happening again.

I just had the same thing happen to me - voltage regulator went poof. No idea why.

Can you show what track you cut on the RAMPS?

I didnt fix the ramps I retrurned it. if you have a shorted power pin dont bother trying to deal with it. its a defective board and no trace being cut will fix it