USB charger - how to check?

[AndrewT]

Hi all.
How do I check a USB charger, before I plug in my expensive equipment?

I have a mains to USB and a 12Vdc to USB pair of chargers.

Which pins are power?
What range of voltage can I expect?
Do I need to draw some current?
How much current?

Can I draw too much current and prevent it switching on?

I am prepared to cut an existing USB cable to expose the wire ends. This can then become the "test" lead.

 

[Osvaldo de Banfield]

Ok. The USB connector has two power lines, a -0V and a +5V, at the extremes of the flat connector. In between, there are two data signals, data+ and data-, you must not use them. Put a small resistance, about say 22ohm to draw aprox 1/4 amper, and check voltage, 5V. If the voltages is 5V, then the chrgr is OK.

https://www.google.com/search?q=usb...gG_6JX_Ag&sqi=2&ved=0CEAQsAQ&biw=1024&bih=705

 

[AndrewT]

Thanks Osvaldo.

 

[AndrewT]

4 chargers checked.
3 perfect
wht=0V, org=5V (I don't know if these wire colours are universal in a USB cable). grn & blu must be data by elimination.
1 smelled strongly of burning.

3working chargers, total cost £4.93 from 2 different suppliers, all including postage.
Ebay works sometimes. Let's see if I get a refund for Dead On Arrival from the 3rd supplier.