I've been having trouble getting my Raspberry Pi to work, and I found out that the power supply I was using had only been supplying 4 volts (give or take half a volt). I bought this one from Adafruit, which is made specifically for the pi thinking it would do the trick, but when I plug in my Pi and use my multimeter on the test contacts I'm barely getting 4.5v. Here's an even clearer image of the multimeter. With my previous power cables I was lucky to get past the initial boot up sequence. With this new one I can at least get to a command line, but attempting anything more intensive than launching vi causes it to overdraw and shut down.
At this point I've tried a number of power supplies, and none of them work, not even the one made specifically for the Pi. I don't know what to try next. Is this power faulty? Could it be a faulty Pi? I've had such bad luck finding a power supply that will deliver enough power I'm starting to think there may be some other issue causing the voltage to drop.