Fix a Fried Arduino Mega

by korostelevm

120K8244

Intro: Fix a Fried Arduino Mega


Sometimes you may do something stupid, other times it is totally inexplicable but as a result of whatever events, the green power light on your Arduino stopped coming on. In my case it turned out to be a burned out voltage regulator.

This inscrutable is a explanation on how to replace it and identify the problem. I couldnt find anything online that explained how to fix a dead Arduino so this may help some people.

(keep in mind that your Arduino could have something else fried, so this wont work in every case)

But also this may work on a regular arduino, if in fact you did burn out the voltage regulator, since they both use the same part.


STEP 1: Looking for the Problem

I was working on interfacing an Arduino Mega with an Irobot Create platform, when for some strange reason i got a power surge on the USB port and the Arduino shut off seemingly for good.

When plugged in, the big overcurrent inductor (in the image below) on the board would quickly heat up, the board wasn’t recognized by the pc and no lights came on.

After thinking what could possible be wrong, the voltage regulator came to mind. It takes whatever voltages go into the power supply and brings it down to 5 volts that is needed for the ATmega chip. The regulator on the board is the: MC33269D-5.0

Go here for the datasheet:http://pdf1.alldatasheet.com/datasheet-pdf/view/12048/ONSEMI/MC33269D-5.0.html

it comes in two packages that do the same thing but look a little different, your arduino may have either one.

STEP 2: What Happened?

To check if the regulator was indeed bad, I used a continuity tester between pins 1 and 2. Luckily I had another working arduino around to compare to. On a working board, there is no continuity, on my broken one, pins 1 and 2 were shorted out.

To further investigate what happened, I refered to the Arduino Mega schematic, available here as pdf: http://arduino.cc/en/Main/ArduinoBoardMega

They also have the eagle pcb file so you can actually see the arduino's design and move things around to see how they are connected. Very useful.


The short in the voltage regulator basically took all the voltage from the usb in a loop over the overcurrent protector and heated it up without powering the board.

I thought since the voltage regulator was for using higher voltage sources with the Arduino, if you took it out, it would work with usb again.

That is one solution. You can totally remove the voltage regulator violently with pliers and the board will work again off USB. But not with any other voltage source in the Vin pin or the 9v jack.


STEP 3: Replacing the Voltage Regulator

For this to work again I decided to put in a new voltage regulator. Here is the picture with the voltage regulator removed (this actually still works off usb)

To put a new one in i needed something with a positive 5 volt output, so the common 7805 regulator seemed to be a good choice. Datasheet: http://www.electrokits.com/Datasheets/7805-Datasheet

I matched up the connections and soldered it in.

STEP 4: Its Back!

The board was resurrected, it is capable of using other power sources like before. Possibly even higher voltages than the original mega was rated for because of the big heat sink.

If you look closely in the photo, you can see the green light is on!

41 Comments

jacka.alice 3 years ago

The fuse is still tripping after removing the (very fried and backend) regulator, any suggestions on where to start looking for the fault?

I fried 2 by giving them 24v, one lights IP for 6ish seconds and the ATMEGA chip gets really hot before tripping, the other lights of a second and dies

SeanMiller 4 years ago

Thanks for taking the time to post. It saved a lot of research.

I blew mine by cutting a cable that was powered from the 5V header. It effectively shorted the regulator to ground for an instant. The damage was such it wasn't causing a straight ground, but rather regulated power down to 1.2V. In turn, I could use the USB jack to power since the regulator wasn't causing the problem.

yashsvnit022 4 years ago

Same thing happened with my Mega.Can you please state reason why your Mega get shorted??

Thanks!

wilbs719 5 years ago

Thanks for the insight, I didn't have a surface mount regulator, so I used a standard 7805 in it's place. Since I don't care about looks, this will do and it should be much more robust than the original. I am reading 5.07 and 3.28 volts without a load. I used some short leads and soldered the leads to the pads on the board. Be aware that the pin-outs are different between the 2 regulators. Still gets hot, so a heat sink is a must.

kgaurkhede 5 years ago

thanks a lot I too fixed my mega board

kumarpraveen 6 years ago

My arduino mega 2560 voltage regulator ams1117 has been burnt due to short circuit
What to do know?

kees.ricken 6 years ago

Awesome, that did the trick for my Arduino too! Thanks for sharing!

DavidH353 8 years ago

Thanks for the pointers. My Mega 2560 has a different regulator than yours. Easy enough, and cheap enough. I just purchased fifty AMS1117 5.0 regulators for $5.40 shipped.

BristolA 8 years ago

My 2650 is used in a 3D printer. A few days ago it decided to run the set up process before each print and then stop dead as soon as it got to the Gcode for the print itself. After replacing all of the plugs and wiring I discovered that if I printed from a stone cold printer, it would print. If I tried to print from a warm printer, eg print two successive items, then it would hang.

I have just discovered this article and I am now wondering if it is the VR that is causing the problem. It's either that or a cold solder joint somewhere, but I have been over my 2650 and my Ramps boards with a magnifying glass, nothing visible that looks bad.

I am wondering whether I can simply snip off the original VR and solder a new to the old legs that can remain in the board. It would make an awkward job a lot easier. I can get hold of LD1117S50TR's, so if the pinout is correct, would this be the way to go?

timekiller_9 8 years ago

BristolA,

If you have a multimeter, check if you're getting 5V on the output pin of the voltage regulator before bothering. It's a difficult job to replace it in any case so doing so unnecessarily will only lead to further frustration.

My popped voltage regulator didn't really look fried, the only suspicious thing was that I couldn't really read the letter/number markings on it, but then I wasn't really sure if I could prior to the frying incident. Visual inspection is not very telling with tiny electronics components, you really need to test it with a multimeter.

The biggest problem I see with getting a new voltage regulator soldered on to the existing pins is simply getting it to sit flat/straight enough to do so on an uneven surface; it's problematic enough to do so once the pads are smoothed out. Similarly, those existing pin fragments are going to slip once you heat them with a new voltage regulator sitting on top, possibly leading to a short. I have to suggest trying, as I say below, to sweep the pin fragments off after snipping the small one and cracking the bigger back plate by repeatedly bending it up and down.

Secondarily, you may not get a really solid solder connection with the old pin fragment there. It could then work for a time, but may come loose if your Arduino is subject to any amount of bumping around. In my case I use it in my car, so a very hostile environment for anything that isn't bolted down really well!

Any Lx1117x50... should be just fine.

Good luck with it.

BristolA 8 years ago

Thanks for the response, but I found a video showing how to check the VR, its definitely cooked. I sent pics to Arduino to see if the board was genuine, but its not, just an excellent copy, right down to the gold chip. I bit the bullet and bought a 100% genuine Arduino, flashed the printer config, and plugged it in. It all worked perfectly.

I will see about repairing the Chinese one, as a spare is always handy to have.

timekiller_9 8 years ago

I figured you'd have looked elsewhere by now, but I thought maybe others might benefit from the feedback. Heck, I ended up here just looking for ideas about why my Mega was fried.

You should try to repair the cooked board. It's good practice and worst that can happen is that it's still toast and ends up getting tossed anyway.

Even though it's a knock-off, I'm somewhat surprised that the voltage regulator went out if the input voltage was within reasonable tolerance. You might actually be better off to try to repair the board, use that as your primary again, and see if your device fries the voltage regulator again. If it does, I'd say there's a good chance you're going to fry a genuine Arduino too!

Best of luck with it going forward.

musthy 8 years ago

Just replaced it !

timekiller_9 8 years ago

Thanks to the poster of this instructable for the hints and encouragement.

I repaired my own Arduino Mega today. Symptoms:

1) Sketch would not auto start without reset at USB plug-in/power-up. Otherwise would generally work well when plugged in to USB.

2) No startup at all under any circumstances with power provided to power plug.

3) 3 plus or minus volts measured at voltage regulator output when 9-12 volts provided to power plug from wall wart.

I heard a pop and smelled electrical fire once while attempting to power the Arduino Mega from a car battery (without any other protective circuitry - I was just starting out and knew much less than I do now).

With all due respect to the poster of this instructable, I do encourage others to seek out a proper SOT-223 5V fixed voltage regulator and not use the old style TO-220 package. If you're going to brave soldering in a TO-220, then you're brave enough to try to solder the proper SMD one. For heaven's sake, don't rip the thing off the board with pliers at least, that's a real shame. Today I used a LM1117-5 that I sourced locally (California south bay area) for $0.75 and it works great. Solved all symptoms mentioned above.

Once you've identified the voltage regulator as a problem, start by using side cutters to cut the 3 small legs of the popped voltage regulator. Raise it up with a small jeweler's screwdriver. Then slowly and gently push it up and down with your finger until the large back plate breaks.

Heat up your soldering iron and heat each of the pads until you can push the left over pieces of pin upwards and ultimately take them off the board. If you're lucky they'll stick to the iron and you can use a wet sponge to just wipe them off the iron. The hardest one is the larger back face. You may need to lie your iron a little bit sideways to melt all the solder at once. In any case, your iron will need to be fairly hot for this to work.

Finally, apply the tiniest bit of flux to each of the pads (use chipquik if you can get it, it comes in a handy syringe which is optimal for this purpose). You can position your new voltage regulator on the board and hold it with your finger nail. Take up a little solder onto your iron and tack down the large back pad. Once it's held in place, you can do the same without a finger nail, using just a tiny bit of solder on the 3 small pins. Just be careful of that one resistor or capacitor or whatever it is near by the voltage regulator, you don't want to damage that with your hot iron.

If you're lucky, your Arduino Mega could be brought back from a voltage overload for very little time/money invested!

Good luck all! Again, thanks to the poster for the hint!

RedstoneM 8 years ago

Depends on what you fried, if you saw a bright flash, chances are low.

TheGreatResistor 8 years ago

nop no flash and i mostly think it happened since i accidently put 5v thru the 3.3v pin hehehe ....

RedstoneM 8 years ago

I burnt a wire on the board and now i must use an external regulator or do it like you (and add external reverse protection diode and capacitor)

humphrey.lees 9 years ago

I cut off the regulator but the short between pad 1 and 2 is still there. Can I still go ahead with the LM7805? or is something else wrong?

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