Bad 5V 1A (1000mA) USB port power supply

[FunkyELF]

Hello,

I bought 2 of these power adapters for my 2 raspberry pi's.

https://www.adafruit.com/products/501

One of them seems to work okay while the other gives me nothing but problems with my keyboard.
My multimeter shows 4.83 on the bad one and 4.91 on the good one.
The 4.83 is within the range specified for the raspberry pi but again... it is giving me keyboard problems.
Keys are being missed and sometimes it is like a key is stuck in the down position and letters keep repeating themselves.

I'd like to set up a return if I could please.

[adafruit_support_bill]

Is that 4.83 measured at the adapter, or at the Pi? Some cables have a lot of resistance so you get quite a voltage drop. Have you tried swapping cables?

[FunkyELF]

The 4.83 is measured at the Pi between TP1 and TP2.
The cable is a standard 3 foot cable, I have not tried a different one yet.

The setup was exactly the same between the different power supplies.
I was booting up the Pi, testing it, then swapping out the power supply.
I tested an HTC power supply that came with one of my phones... it reads a constant 4.86 but does not cause any keyboard glitches.

[adafruit_support_bill]

It's hard to believe that -0.03v is causing keyboard glitches. But it could be noise from the switching regulator. We can try replacing it. Contact support@adafruit.com with a link to this thread.