Fried Mega 2560 with RAMPS 1.4

Hi, I just finished building my 3d printer using the arduino mega 2560 board with a ramps 1.4 board.

Uploaded the marlin firmware to the board via usb, then plugged in the 12v power supply.

As soon as the power was connected, magic smoke started coming from the mega, so I unplugged it.

Touching the usb cable, it was very hot, and upon further inspection, I saw that the component circled in the image was fried.

What is this component? and can I repair it?


Hi, welcome to the forum.

I didn't check the schematic or the board layout, but that might be a mosfet that is used to turn the USB power off, when power is applied to the power jack. How did you connect the 12V ? Only the power jack (DC power barrel jack) or the VIN pin. What kind of 12V was it ? DC or AC, 12V or 18V ? An unregulated 12V power supply could have an output of 18V without load.

It should not smoke, because there is a 500mA polyfuse next to it. Is it an official board ? If yes, which offcial version ? the or the version ? Perhaps there is a shortcut on the board. Was the power supply to the power jack 6V or 7V, instead of 12V ? A voltage below 7.5V does not turn off the USB power.

You could remove that component. Use a big blob of solder and heat all three pins, it should easily fall off. Perhaps you could use a magnifier to check for shortcuts. After that use 7.5V to the power jack, and measure the 5V pin and 3.3V pin. If they are okay, increase the voltage to 12V.

However, there might be something else that is damaged on the board. This Mega board is no longer reliable.

Peter_n: snip

Thanks for the quick reply Peter!

Just measured the supply voltage, it was 12.5v DC

Power was provided through the RAMPS 1.4 board as instructed from the reprap website.

It is a sainsmart knock off board from ebay, I will be contacting them shortly.

I have removed the component, however it will now not power up from usb, is that normal?

I will now check all of the pins and get back to you.


Here is a photo of my board.

As you can see, I have removed that chip as it was fried.

Upon further inspection, it looks like there could be a tiny tiny hole in the chip circled on there.

I have applied 12v to the barrel jack and confirmed that it is outputting 3.3v and 5v correctly, however it is not being recognized by my pc when usb is plugged in. Could that be caused by this chip?


The component is probably a mosfet to turn on/off the USB power. If you remove it, only the power to the power jack will work. So it won't power up with USB power anymore.

What about the metal case of the crystal ? Is that touching some solder of the components next to it ? The crystal is the shiny metal up-side-down bathtub with R16... on it.

Yes, that square chip is the interface between the usb and the serial data to the ATmega2560. If the board is no longer recognized, that chip might be blow. I assume that also the comparators are damaged (a comparator is used to drive the mosfet for turning on/off the USB power).

This is the black sainsmart Mega R3 :

Try to get your money back. I think it was a bad board.

Hi to all!
I’v got a problem with sainsmart 3D printer kit too (Mega 2560, A4988, Ramps 1.4)!
Firstly, my motors won’t move at all. And there is a problem using the 12V power supply and USB together. When setting the current form the driver it seems that when pluged in the USB Vref = 0,28. When is on the 12V power supply only, Vref=0! When both are pluged its 0,26.
I am a newb with Arduino but I think in both cases Vref must be equal.
5V and 3,5V pins are good.
When cheking motor power supply with USB is 0,12V and with 12V power supply is 11,84V, so my driver is not dead, right?
My power supply is 12V 5A for LED with real 11,86V. But I may change it.
When both USB and 12V are pluged, the Arduino board is visible for the PC. I can upload programs, the LEDs are blinking but no motion from the steppers.
Maybe I lost a COM port too.
It is most probably the voltage regulator causing this, but I’d like to be sure from you.
Also I can’t use my LCD now. See how they mounted the smart adaptor.
In all photos and tutorials the connectors, or what ever you call it are facing one direction!
And…it turns my motors are 2A! Could I power them with A4988? As I know they give 1,6-1,7Amps!
What is the most painless way to solve this?