Plugged RAMPS power in wrong. Magic blue smoke escaped.

I just accidentally fried my RAMPS 1.4 board by plugging in the PSU without being careful, and the plug was offset by one to the left. Needless to say there was smoke and now the board is dead. Fortunately the Arduino is still fine. I can see that one of the Resettable Fuse Polyswitch packages (F1) has a brown spot, so I've ordered a new set of those in the hopes that all I need to do is replace this one - or possibly two - components.

Has anyone else encountered this kind of issue in their RepRap or electronics career, and how likely is it that only the components near the power plug are fried?

Edited 3 time(s). Last edit at 03/12/2013 07:27AM by Thinkyhead.

There are 2 x 12V inputs on RAMPS.

1 x 11A input, which is connected via the MFR1100 PTC fuse F2 to the FET Q3. This is the one that drives the heated bed, and it's "possible" that having it backwards could lead to frying pin D8 on your board. That said, I think that part may be unlikely, but you may need to replace the FET Q3.
1 x 5A input, which is connected via the MFR500 PTC fuse F1. This then runs the remaining 12V for the entire board (hot end, fan, pololu's, the Mega if you have D1 installed). There is however a diode marked D2 that is placed across this which, if you put the voltage backwards, should limit the max reverse voltage to -0.6V on all those components and draw a large amount of current in the process, tripping/blowing the PTC fuse. The Mega is also further protected by diode D1.

In short, if you replace the damaged PTC fuses you should be fine, however, I would check Q3, the Mega output D8, and D2 may also need to be replaced. I personally prefer real fuses instead of the PTC ones, but they are useful none the less.

Note: The PTC fuses are in my opinion slow to fire and annoying. By being slow to trip, IMO they can lead to other components failing that normally wouldn't. In this case, D2 could be put under more strain than necessary, as well as the tracks on the PCB that carry the voltage from the connector to the PTC fuse F1, from F1 to D2, and the return from D2 back to the connector. Also, I've seen PTC fuses catch fire if they're given a significantly high current to try and block. While they definitely "blow", the fact that they actually can catch fire in the process worries me.

FWIW: The Schematic is useful here: [reprap.org] - The relevant areas are "Power" and "Heaters & Fans". They're the ones dealing with all the components I mentioned.

The polyfuses should reset themselves, though I've never overloaded them that much.

You might not need to replace the polyfuses, because the short circuit happened before the current went through them. Can you post some pictures of the damage (top and bottom of the board please) and if there is any heavy black smoke damage if it can be wiped off that would be helpful too

It might be enough if you surgically added some wires to extend the power pins on the board. If you post pics and this is the case, I can photoshop some wires in to show you what I mean.

Actually it turned out the polyfuse was probably fine. I replaced it anyway. In the process I discovered that the D2 diode was cracked, and this is the component that smoked when I plugged in the board. Since it burned up when I plugged in the board correctly, I'm now unsure whether I ever really plugged it in wrong. Anyhow I replaced the diode and now all is well!

I just did something very similar, and let the smoke out of something on my board.
I was trying, stupidly to manually turn on the fan by connecting two jumpers to it and to the ramps board while the board was on.
Needless to say, I did something wrong, and a bunch of white smoke started pouring out.
I want to see if it is the ramps board or the the mega that is fried, but I can't figure how to separate the ramps shield from the mega

Maxwellfire:

First thing is do it slow and carefully.

I tend to lever up a side slowly at each corner no more than 1mm at a time. Start on the corner the D8/USB connectors are on till you see pins between the board and the socket. Then work clockwise (looking down) from there (corner near the end stops, corner near the Z driver, then corner near the power connectors. On either your second or third time around the board should come off, so be careful not to bend any pins if it sticks on one side.

FWIW: I use my thumb and the pointer finger to push the boards apart. I place the thumb on the bottom of the RAMPS board (pushing away from the Mega) and then I put my pointer finger on the edge of the Mega, but with both thumb and finger touching a fair bit. This gives you good leverage while the fingers touching each other slows you down so you don't overshoot and bend pins (it gives you additional control of how much force you're applying). If you still have issues, you can use something else to lever them apart (eg: a standard wooden clothes peg). Put the closed end between the boards then twist slowly to push them apart. If you use a lever, make sure that it's not going to damage the PCB's (eg: wood, or if it's metal, it's covered in tape), and NEVER do this while either RAMPS or Mega are powered!

Hope this helps.

I did the same thing.

REPLACE Diode 2

What happens is the 12V shorts out through Diode #2 as the least restive path, and burns it up due to no resistance.

Edited 1 time(s). Last edit at 07/25/2013 11:39AM by ShadowRam.

Quote
Thinkyhead
I just accidentally fried my RAMPS 1.4 board by plugging in the PSU without being careful, and the plug was offset by one to the left. Needless to say there was smoke and now the board is dead.

Hi,

I also could not save the smoke. :-)

I connected as shown in the image here. I left the first terminal and connected on subsequent terminals on the SMPS. Is this wrong , if yes why ?

The way you have it wired is fine as long as you have the white wires going to the printer in the - and the pinkish wires going to the + terminals. Make sure that the voltage selection switch for the SWPS is set to the appropriate voltage for your area, and the trim pot is dialed in for the appropriate output voltage.