Author Topic: Using Small Guage wire to power backlight LED?  (Read 569 times)

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Offline sherminnater

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  • Posts: 3
Using Small Guage wire to power backlight LED?
« on: Fri, 11 January 2019, 13:27:32 »
Hello, Im building a KBD75 rev 2 and 3 of the backlight LED's (Behind the key caps) do not work, after poking around and looking and the PCB diagram, I've come to the conclusion that a 2 resistors are not functional, it looks like solder contact is good. These resistors are not the through hole style and I don't feel like I have the skill or equipment to replace them. So what I was thinking was running some thin gauge wire from an unoccupied LED solder point to the LED's that do not work.  Does this sound like a good plan to anyone? I don't want to ruin my whole PCB, I just wanted to make sure this sounded reasonable.

Thanks in advance!

Offline tex_live_utility

  • Posts: 590
Re: Using Small Guage wire to power backlight LED?
« Reply #1 on: Sun, 13 January 2019, 09:42:35 »
You need those resistors to get the correct LED brightness. If you bypass them you will need to use your own resistors.

Unless they are very small, it's usually easy to remove surface mount components with desoldering braid/wick.

Offline OldIsNew

  • Posts: 125
Re: Using Small Guage wire to power backlight LED?
« Reply #2 on: Mon, 14 January 2019, 21:59:41 »
You need those resistors to get the correct LED brightness. If you bypass them you will need to use your own resistors.

I'm probably stating the obvious, but just in case - to be clear you don't just need the resistors to get the correct brightness - you need the resistors in order to not almost instantaneously burn out your LEDs. If you just hook up the LEDs to power and ground (with a typical 5V setup) without an appropriate resistor they make a nice flash and that's it. Just adding this out of caution.
 

Offline pixelpusher

  • Posts: 2929
  • Location: Tennessee - USA
Re: Using Small Guage wire to power backlight LED?
« Reply #3 on: Mon, 14 January 2019, 22:21:28 »
You need those resistors to get the correct LED brightness. If you bypass them you will need to use your own resistors.

I'm probably stating the obvious, but just in case - to be clear you don't just need the resistors to get the correct brightness - you need the resistors in order to not almost instantaneously burn out your LEDs. If you just hook up the LEDs to power and ground (with a typical 5V setup) without an appropriate resistor they make a nice flash and that's it. Just adding this out of caution.

Don't forget the smoke.  There will be pretty smoke too.  Fun game, take a button cell (1.5v) battery and touch one leg of an LED to the top and one to the bottom.  Now you can test your led color.  Keep adding batteries in the stack (usually 3) until you get a nice snappy pop and blue smoke. 
:)