Save A Fried Arduino Mega

An Instructable by korostelevm

Arduino Mega
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I wasn't able to find anything online that explained how to fix a dead Arduino so I'm hoping this may help others in a similar situation. Remember, your Arduino could have something else fried, so this won't revive every dead Arduino.

Step 1: Troubleshooting Your Arduino

While I was interfacing an I-robot Create platform with an Arduino Mega, I got a power surge on the USB port and my Arduino shut off. When I plugged it in, the big over-current inductor (in the image below) on the board would quickly heat up, however the board wasn't being recognized by the PC and, sadly, no lights came on.

After thinking about the possibilities, the voltage regulator came to mind.

The regulator takes whatever voltage goes into the power supply and brings it down to the 5 volts needed for the ATmega chip. The regulator on the board is the MC33269D-5.0.

Voltage regulator/Over current protectorVoltage Regulator/Over Current Protector
Test with a continuity testerTest with a Continuity Tester


Use this link for the datasheet. It comes in two different packages. Both do the same thing, but they look a little different. Your Arduino may have either one.

Checking further to determine if the regulator was indeed bad, I used a continuity tester between pins 1 and 2. It was nice to have another working Arduino around to compare it to.

I noticed that on the working board, there was no continuity. But, on the broken one, pins 1 and 2 were shorted out. To further investigate, I referred to the Arduino Mega schematic.

Arduino also has a very useful eagle PCB file where you can actually see the Arduino's design and move things around to see how they are connected.

Shortage loop Shortage Loop

I realized that the short in the voltage regulator basically was taking all the voltage from the USB in a loop over the over-current protector and heated it up without powering the board.

Since the voltage regulator was for use with higher voltage sources with the Arduino, I thought if you took it out, it should work with the USB again. You could also remove the voltage regulator with pliers and the board would work again. But, not with any other voltage source in the Vin pin or the 9V jack.

Step 2: Voltage Regulator Replacement

I decided to put in a new voltage regulator. With the voltage regulator removed, it still worked off USB power. To replace it, I needed something with a positive 5V output, so the common 7805 regulator seemed to be a good choice. I matched up the connections and soldered it in.

Ripped out regulator Ripped Out Regulator

Step 3: It's Alive! Arduino Mega Back In Business

The board was saved! 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. Look closely at the photo below, the green light is on!

Green Light and the Frankenregulator Green Light and the Frankenregulator



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