Fried Mega 2560 with RAMPS 1.4

So I have a reprap prusa i3, that came with a ramps 1.4 and arduino mega 2560.

I managed to upload marlin to the mega without external power connected, then connected my psu, which made a pop noise and smoke came from the Megas USB chip.

I thought something might've been wrong with the mega so I ordered another, double checked all connections to the ramps and tried again, when the same thing happened.

Then I ordered another mega and a new ramps. Moved the stepper drivers over from the old ramps to the new one and tried again. This time there was no smoke or noise, but the USB connection failed to be recognized after.

In all 3 cases, whenever my external psu was connected and USB connected, the USB cable would get extremely hot. I'm assuming there is a short somewhere but not sure where.

Could one of the stepper drivers be borked and cause this? Or something else? What can I do to troubleshoot?

Thanks!!

PHOTOS: [imgur.com]

Test the Mega board without RAMPS. Can you see it on your PC? Can you program it with ArduinoIDE?

I would disconnect everything from the RAMPS ( Drivers, extruder, heatbed, temp-probes etc. )
Check the connectors of the RAMPS and Mega to find any solderbridges or other shortcuts. On one picture the heatsinks of the MosFets are connected. Change that
Then check the polarity of your PSU connector again. ( 12V DC? ) Your pictures didn´t show the powerconnector with the bridges?!

If that´s OK, put the Ramps and Mega together and use only the power connector. No smoke?

You have to switch the PSU off everytime before you work on the RAMPS!
Start poulating one driver at a time, adjust the potmeter ( switch PSU off ) and connect it with one of the steppers ( without beltpulley attached to see it running freely)
Use the smart LCD to move the stepper back and forth. Runs smoothly? OK, next driver/same stepper.

Then connect the endstops one by one. Check the manual for the right polarity. ( Some guys have reported wrong cable connectors/colors! Check twice !)
Does the LED get on, when you press the endstop? OK, next.

Check the heatbed connector. Is it done for 12V? ( both GNDs connected? ) Yes, connect it to the RAMPS together with the tempprobe( Power off first ) and use the LCD to "preheat PLA/ bed ".
See the temp rising on the LCD? OK.

Connect the extruder and it´s tempprobe and see if that works by "preheat PLA".
Now you have only the fans left to test and if everything works, you can connect all steppers and pulleys to make a testrun.

Use the SD-card to print a gcode-samplefile.

When everything works, you can try the USB cable again...
Good luck
-Olaf

The USB cable getting hot might also be due to some ground loop. So make sure that there is no significant voltage difference between the ground of your PS and the ground of the USB. Measure the voltage between the two grounds *before* both are connected via the controller. Is your PS connected to the same AC outlet as your PS?

Interesting I think I just had the same problem as this, although I haven't gone an purchased another board yet. Everything was fine until I plugged in both the power AND the usb, then pop hiss! Did you figure out the issue OP?

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enif
The USB cable getting hot might also be due to some ground loop. So make sure that there is no significant voltage difference between the ground of your PS and the ground of the USB. Measure the voltage between the two grounds *before* both are connected via the controller. Is your PS connected to the same AC outlet as your PS?

So should they or shouldn't they be on the same outlet? Personally my PS was directly into the outlet, then my computer was plugged into a UPS which was plugged into the same outlet.

How about a Laptop PSU? They should be isolated or not?

My concern is more on the Mega board: There are several power-routes ( 12V barrel-connector vs. 5V USB ) that "should" disable each other, But when they fail, it can get smelly.
IE. when the USB voltage is too low or any of the components has a bad solder contact, it can fail.

-Olaf

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gatorNic
Interesting I think I just had the same problem as this, although I haven't gone an purchased another board yet. Everything was fine until I plugged in both the power AND the usb, then pop hiss! Did you figure out the issue OP?

Yup manage to work out that my psu wasn't grounded correctly, causing the voltage to be seen as wrong by the mega. Solution was to manually connect a cable between V- and ground on the psu.

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tommy-b-10
Yup manage to work out that my psu wasn't grounded correctly, causing the voltage to be seen as wrong by the mega. Solution was to manually connect a cable between V- and ground on the psu.

How did you figure out that it wasn't grounded correctly? So you put a wire between an open slot V- and the ground or did you wire it to the V- slot that was going to the MEGA? Although probably wouldn't matter I would guess.

Good to here you got it up and running! That's my worry is to order another board without solving the problem first. Need to do some testing.

Quote
gatorNic

Quote
tommy-b-10
Yup manage to work out that my psu wasn't grounded correctly, causing the voltage to be seen as wrong by the mega. Solution was to manually connect a cable between V- and ground on the psu.

How did you figure out that it wasn't grounded correctly? So you put a wire between an open slot V- and the ground or did you wire it to the V- slot that was going to the MEGA? Although probably wouldn't matter I would guess.

Good to here you got it up and running! That's my worry is to order another board without solving the problem first. Need to do some testing.

I´d use an ohm meter to measure resistance between V- of the PSU and GND on the RAMPS. Should be Zero..
-Olaf

I just had the SAME thing happen to me.

USB powered up fine, all endstops/stepper controllers/wiring was 100 percent correct.

As soon as I powered up the PSU on the printer, Laptop shut off and the USB chip on the Arduino released it magic smoke.

I unplugged the mains power, checked the Ohms between the ramps board Neg and the Ground, 0 ohms...

Any ideas on where to start when I get another Arduino?

Thanks in advance.