I have 2 keyboard U9BL and it both have some LED dead and I come up with a plan to replace those led.
Let say I have the keyboard name A and B.
Thing goes after I put another LED in the A keyboard, I don't know if I did something wrong, but all the led of that keyboard is off no matter I try to increase the light level. I thought maybe those LED are dead so I want to test it by taking 1 good LED from the A keyboard and put it in the B keyboard and that LED is still fine. I try to test 2 more LED from A and all of them are fine. Now, the B keyboard is ok but the A keyboard is still can't turn on those LED.
So the problem is that I don't know what is the problem with my A keyboard. I plug in and test all the key, it's fine. Everything is fine except the LED doesn't turn on. I need you guys to tell me any possibility that is happening to my keyboard and I will try to test that possibility and if it's it, I'll try to fix that later. The priority task now is determine the target, after that I'll have a strategy to eliminate the target

Sorry for my bad English, it's not my mother tongue.