I bought a brand new Raspberry Pi. It came with a 5v ~ 1A power adaptor and a mini-usb cable. I plugged it in and plugged in my cat 5 into the ethernet port. The raspberry powered up but the Ethernet LEDs were not lighting up. After trying a lot of different things I decided to replace the mini-USB cable with a phone-charger cable. And it worked!! The ethernet LEDs came on. Mind you, I was still using the power adaptor that came with the Rasp Pi, I just replaced the Mini-USB cable. Can anyone tell me what was the issue here? Do mini-USB cables have varying power rating or grades? What did I miss here? Please help.


2 Answers 2


Some possible issues:

  • You might be using a usb extension cable. USB looses power with range.

  • The power adapter might say 1A, but can be lower then the label says.

  • Try to disconnect so that both USB ports are available. If you have a usb-wifi dongle or something else that is consuming power, then you can have weird power issues.

Additional info:

  • You can get Micro USB adapters in a range from 0,5 to 2,1A. (Reference)

  • Model A ratings: 300mA. Model B ratings: 700mA. (Reference-A, Reference-B)

  • If you want a simple way of measuring how much power a USB device is using, you can buy THIS device with free shipping. (5,99USD)


basically cable should not matter, most probably it will work fine if you switch cables back.

if it does not -- you have another working cable, use it. could be a bad contact issue or higher resistance of the old cable -- there are just too many different factors to speculate about.

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