Blown RAMPS board

Last weekend while trying to resolve a problem with the extruder on my new build RichRap 3DR I occidentally connected the power connector one pin over to the right, thereby swapping power and ground on the 5A feed. Needless to say the magic smoke escaped.

Now when I connect the board to my bench supply it is a dead short and fails to start. However I cut one of the legs on diode D2 and it now seems to boot.

What is the function of D2?
Is it likely that I have blown D2 or if not what else might have gone pop?

Cheers

Z

D2 is polarity protection.

Its ment to blow when you do just that to save the rest of the board (sadly it doent survive)

Replace D2 an cross your fingers

I'd also double check operation of the smaller polyfuse. The dead short likely released the magic smoke of the D2 before the fuse was affected, but the short may damage the internal composition so that it doesn't operate as it normally would.

Dust: Thanks for that, Have now replaced D2 and the board appears to function OK.

cdru: What is the best way to check the smaller poly fuse?

Z

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I guess it wasn't so much to actually check it aside from a basic continuity test, but to be aware if you have issues still. If it is damaged, the resistance should increase and may trip at a lower current then previously. The spec sheet says that at 23 deg C the resistance should be between .01 and ,03 ohms. If you haven't powered it in a while (a "cold start" so to speak) and it's outside that resistance, I'd replace it.

cdru: checked the resistance, both with the RAMPS board connected and disconnected, but with the polyfuse still in place and I get 0.6 ohms. Do you know the spec of the part or a manufacturers part number as I cannot seem to find a BOM which tells me and I will get some and replace it anyway. It would be nice to have a spare board.

Z

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My blog: 3DR build and more . . . .

About half way down the Bill of Material is F1 and F2 with links to Digikey where you can find spec sheets or order replacement parts. Some people have replaced the polyfuses with fuse holders and use automotive-style blade fuses in their place.

cdru: Once again thanks for that, I found that page but didn't see the BOM. Need to stop looking for this stuff last thing at night!

Z

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