[blahbear]

I got a non-backlight keyboard, but it actually came with LEDs, just not powered up. So I soldered a USB cable to supply power. (detail in this post http://www.overclock.net/t/1031531/my-first-mechanical-keyboard-xarmor-u9-plus-cherry-blue-impressions/30)

It works fine when I plug it into a desktop PC, but I got "Power Surge on Hub Port" on a laptop. I know that the problem is the LED is drawing too much current, and I think adding a resistor should help, but I'd like some expert advise on this before I start working.

Is adding a resistor enough?
How do I know how much resistance I need?
Anything else I need to look out for so that I don't damage my motherboard?

Thanks!

 

[just_nuke_em]

Unless you know the forward voltage on the LEDs, their current draw, and how they are configured (series/parallel and how many), you can't really find the ideal resister off hand. I'd recommend taking a 500ohm potentiometer and putting it in series with one of the power wires. Start with the resistance turned all the way up, and adjust till you like the brightness.

There could be other things going on here, but you didn't provide that much info to really troubleshoot it.