Power is good - I've tested with a voltmeter. According to this link, the SD card image is not written properly yet:

The Raspberry Pi cannot find a valid image on the SD card. Check card is inserted correctly.

The OK LED does flashes once. Is this to be expected if SD image is bad? I think this is because I took the SD card that was formatted FAT95, and dd is choking on it somehow. I will delete all /dev/sdb partitions via fdisk.

I'm pretty sure this will get the SD card happy again (at work now - so, have to wait a few hours to test), and dd can then write the image cleanly to a blank SD card. Just curious if anyone knows for sure that OK LED does flashes green once in such cases while the Pwr LED stays solid red, but no video, when there is bad SD disk image inserted.

Thanks for any ideas....

  • Welcome to SE. Please see raspberrypi.stackexchange.com/faq#signatures and meta.stackexchange.com/questions/2950/…
    – XTL
    Commented Dec 11, 2012 at 7:45
  • " I think this is because I took the SD card that was formatted FAT95, and dd is choking on it somehow. I will delete all /dev/sdb partitions via fdisk." Deleting the partitions on the SD card will not help. If the card is still formatted as FAT, then you are going to have to reformat it to use a Linux filesystem, such as ReiserFS (not recommended), or an extended filesystem such as ext4 (highly recommended). Out of curiosity, how did you write the image? Did you use the Windows flash utility or write the image using dd from Linux or OS X?
    – fouric
    Commented Dec 11, 2012 at 18:25

5 Answers 5


In my experience, Yes, if the green LED flashes just once then stops, this indicates that the SD card is corrupt. Sometimes it doesn't even flash once, though.

  • True! I was able to dd via a powerbook; linux may have some issues with previously formatted SD cards, and couldn't get dd to work on it.
    – Patrick
    Commented Dec 12, 2012 at 2:59
  • thats exactly what I found, the sdcard was dying and would work intermittantly Commented Jul 30, 2014 at 15:17

I swap cards all the time, try writing another card with the win32 disk imager using one of the distributions like the debian squeeze one. I have 16 pi's and originally used the element 14 distribution but any 16/32 Gb card from sandisk works 2-4 times faster. None of my cards had any issues.

  • 1
    That's not what he asked. He wanted to know if the flashing-once green LED means that the SD card is corrupt. Mind you, I'm not surprised at the confusion.
    – recantha
    Commented Dec 11, 2012 at 6:20

Which Rasberry have you got?
And wich distribution?
I tried starting an new 512Mb Model B with an old rasbian image. No go!
Downloaded the newer 2012-10-28-wheezy-raspbian.zip and it booted up. Just saw there is an even newer version:



I have found occasionally that corrupt SD cards sometimes have the green OK LED flash once at proper brightness, and then have the appearance of being extremely dull (very hard to see, but not quite off), almost looking like a light bulb filament when there is not enough power to light the bulb properly.

I presume this is due to it coming on for an extremely brief period and then going off again at a regular interval, quite why it does this though I have no idea (I have seen three cards do this now across two different Raspberry Pis).

  • This is probably more useful as a comment, than an answer to the original question.
    – kolin
    Commented May 15, 2013 at 7:38

Solved it.

Had LED blinking twice. No display.

Format card and flash Raspbian with Pi Installer from Terminal.
Boots perfectly!

SD Formatter (Mac + Win) https://www.sdcard.org/downloads/formatter_4/eula_mac/index.html

Pi SD Installer by RayViljoen:

(2015-02-16) Raspbian-Wheezy
Rev B RPi

  • Please try to frame your response in English sentences rather than bullet point it like you have done. It makes it easier to read.
    – recantha
    Commented Apr 20, 2015 at 13:08

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