[Mike] picked up a cheap USB hub for four pounds (about $6) including delivery. He wanted to know how it’s possible to get quality electronics for that price, and as you may have guessed it’s not possible. He cracked open the power supply that shipped with the hub and hooked it up for some testing.
The wall wart has a sticker on it that claims a rating of 1 Amp at 5 volts. It’s pretty easy to see that this hardware cannot meet that spec just by looking at the circuit board. It’s a low-end single sided board that has some really disappointing isolation between the mains and regulated side of the circuit. As far as we can tell there’s really no reliable regulation circuit on the low side of the transformer, and the tests that [Mike] runs in the clip after the break show this. From left to right in the picture above you can see voltage at the hub-side of the power cord, current on the load, and voltage leaving the circuit board. At just 560 mA the voltage the USB hub is receiving has fallen below 3 volts!