Picture of 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.

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Step 1: Looking for the problem

Picture of 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?

Picture of 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

Picture of 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!

Picture of 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!
humphrey.lees4 months 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?

Gelfling66 months ago

I ran into another form of fail on a Mega a week ago.. I somehow corrupted the Bootloader, and had to follow a instructable on here, to reburn the bootloader back into the 2560, using a spare Duemilinova as the ArduinoISP (Files/Examples/ArduinoISP)... It takes roughly 2-3 minutes to reburn the bootloader this way, and despite how everyone else has been using their mega to reburn the ATMEGA328's, even the lowly 168 will program the 2560..

StickyC1 year ago

For what it's worth, I *believe* the LD1117S50TR is a drop-in replacement. The pinout and current/voltage specs look the same and it's in the same SOT-223 profile as the existing voltage regulator. They're $.50/ea in small lots on E-Bay. It's a tight spot for de-soldering/soldering, so folks who are uncomfortable with soldering might do better with the big chip.

I've smoked mine the same way and will let you know how the replacement turns out.

Fabsterdam StickyC11 months ago

I just repaired a fried Arduino Mega with just that part (LD1117S50TR) so I can confirm that it is indeed a drop-in replacement. It sure looks a lot better than the 7805 in the original instructable ;).

bblackhat1 year ago

I repair it with a 7805 but pinout is different..... in 7805 is 1 Vin 2 And 3 Vout

ben0meyer1 year ago

so, for qualification, the over current protector doesn't need anything done to it

varundev1 year ago

I have a arduino uno R3. I accidentally shorted the digital I/O pins while testing a rover that I created. Now the uno is not detected in my computer, but the green power led and the pin 13 orange led light up, so I know its not the regulator problem. Is there any hope?

mnhpias1 year ago
I have arduino mega 2560 R3 . In my case the power led lit up after connecting with source or connecting usb cable with PC but arduino doesn't rspond and PC dont recognize it . what should I do for troubleshooting ? after connecting power , the avr 2560 have been getting hot . pls help me
-max- mnhpias1 year ago

If you can replace the aVR chip, do that. solder wick might help take solder off the SMD. You can put a new one on with a reflow oven. (These can be made with a spare arduino, thermocouple, and toaster oven.)

-max-1 year ago

Why did you just rip off the old regulator, it should've have been desoldered so the pads don't lift off. That way the replacement SMD regulator can be put back on for a elegant fix. You can probably find good SMD voltage regulators on old circuit boards, they can be identified because they will often have a few smoothing / filtering electrolytics night next to them. I found one that is rated 5-7A at 5V, quite powerful, although it was a linear regulator, which made me question that current ability when mounted on a standard PCB.

DigitalOSH4 years ago
Just touched my UNO to the shell of my metal macbook pro... thought it was shot. Thanks for helping me save my brand new purchase (came today!)
Chowmix124 years ago
It doesn't have to be ugly.. I made mine parallel to the board with some creative soldering.
korostelevm (author)  Chowmix124 years ago
Great job! Looks awesome! Did you use the instructions?
Yep, the i'ble helped with the pinouts... Thanks!
I think id probably run that regulator off board, that looks really ugly. but heck, it works. Good way to save a 50$ board:)
nagkiller4 years ago
you could also buy an smd 7805 and put it on it would look better
korostelevm (author)  bigbodysmallbrain4 years ago
I just had the 7805s on hand at the time, if im buying a new regulator i might as well just get the exact one that was on there originally lol

plus its weird now the original regulator had the pins arranged (the ground isnt in the middle) , the surface mount 7805 would have the wrong order and its impossible to twist those things around to match them up like with the big 7805 package
oh i don't have that proplem as i work at a place that repairs laptops and cellular phones so i can "barrow" the parts
oh man thats ugly! but hey if it works, thats all its gotta do! next time before you do this (because i know you will cause itell get broken off ) trim the leads down and try to make it work as if it were a smd component it'll last much longer
Nice work! I have a dead arduino dueminalove, im pretty sure the problem is the atmel 328p-up I'm planning on getting it fixed by/after Christmas.
TOCO4 years ago
Cool instrucable. when I saw the picture of it fixed i couldnt help myself. I bust out laughing at frankenregulator. But hey if it works you just saved yourself $60 on a new arduino mega.