I purchased a 4 digit 7 segment display from adafruit and got it working on my old model A running adafruit occidentalis operating system. I recently bought a model B+ and installed the latest version of rasbian. I went through the instructions to enable i2c, installed python-smbus, and i2c-tools, and can run i2cdetect. However, I was never able to make the display work with the model B+, can't even see it on i2cdetect, just get UU in a couple places because it's looking for some wolfson card that I don't own.
I have been working with Adafruit tech support but they have stopped responding. I measured voltages on the GPIO pins the display uses, and everything looks right except the scl pin, which should give 3.3v, but instead gives almost 0v. I was concerned the pin might not be working, so I ran a script adafruit gave me to turn the pin on and off every 2 seconds, and I measured the right voltage while doing that, so I think the pin is ok, but still not working right.
Since the display lights up on the model A, I don't think it's a soldering issue. Since adafruit tech support has stopped talking to me, I thought I'd try here. Let me know if there are any commands I should run or files I should check and put the results here. I'm not an expert at this and don't have the time to become one, I'm supposed to be writing my thesis.
Here is an image of the pins on the B+. I flagged them to easily identify them. Red is VCC, Yellow is SDA, Green is SCL, and orange is GND. Adafruit never said it wouldn't work on a B or B+.
Finally got this fixed. Had to replace the raspberry pi, the pin was damaged. The display worked immediately when I got it on a new computer with a working pin. Sorry about the delay.