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Corrupt SD Slot? Canon 5D MK3 won't turn on.


I've had a strange issue happen several times in the past two months. My Canon 5D MK3 isn't even 2 years old at this point, and I'm the only owner.


Suddenly one morning before a wedding - my 5D MKIII would not turn on. After removing the batteries, including the clock battery, and waiting a while, I was able to reset the camera. After various tests, I've narrowed this issue down to introducing the SD card.


It doesn't matter if I have zero cards in my camera or a CF card already inserted - when I insert any SD card I have (I only use Sandisk Pro Extreme cards), my 5D will shut off and won't turn back on. I can insert the same SD card into my Canon 6D and I'll have no issues. Sometimes rather than shutting off, it will allow me to access the Quick Screen and menus, but will not fire.


Has anyone ever experienced something like this?


I'll bet! Glad it came back on.

Hi,  I had the same thing happen. I've owned my second hand 5D Mark iii for several years. Love it, no problems, always worked great. Recently, I introduced a brand new Delkin Advantage SD UHS-I Memory Card. I have never used a card in the second slot before, but as a long time pro I really want the back up. Camera off when inserting, turned on, formatted SD card, CF card that had been in camera still there. I took about 15 shots, write speed seemed fine for my use. Cool. Set to go, right?

Later, I wanted to take a few shots. Thankfully it was not a job. Camera would not power on. Turned switch on and off, nothing, took main battery out, and back in, still nothing.  A bit later I put a different battery in, it turned on. 🙂 Then, I turned it off, and on again and it would not power on. 😞 


I googled, and found this post. I took out the battery, clock batter, removed the lens, and all cards. Let it sit for 30 minutes, replaced both batteries,  it still would not power on. Being busy from just returning from out of town, I let it sit a few days. Before I called Canon, I thought I would put a battery in and check it. Yep, it came on! I have since powered it off, on, off, on, taking a few shots several different times.  So far, it is still working. I am not totally trusting it though. Thankful for a backup camera. May need another one. 


I am posting this because the previous posts really helped me. If I find out more defininte information, I will post it. 🙂



Are you using a full-size SD card or a Micro SD card with an adapter?

It is  a brand new Delkin Devices Advantage SD UHS-I 32 GB Memory card, full size.

@CPortraitArt wrote:

It is  a brand new Delkin Devices Advantage SD UHS-I 32 GB Memory card, full size.

Not my brand of choice for memory cards.  I only use Sandisk, and Lexar when I cannot get Sandisk.  If you bought your memory card on Amazon or eBay, then that could be the problem.  I suggest that you visit a local Best Buy, and purchase a new memory card, as well as a card reader to test you Delkin card.


[EDIT] Buy a USB cable for the card reader, if you do not have one.. 

"The right mouse button is your friend."

And sometimes, even an Ebay or Amazon "bargain" or conterfeit SD card isn't what it appears to be... Robot tongue