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Question About LED Reset / Power / Turbo Lights

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Smack2k

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I am in the process of removing the 3 small lights that were used for the Reset / Power / Turbo in my 486 case to replace them with new LED Lights as the old ones dont work any longer...

For the wires themselves that attach to the lights, each set has a color wire (Green / Red / Yellow in this case) and a white wire....am I correct in assuming that the color wire is negative for these and the white wire is the positive? Want to be sure before I solder on the new lights to the wires....
 
I don't think I've ever seen an indicator LED on a case assembly go bad, much less three of them. Are you certain that this is the problem?

Aren't most motherboards set up for individual leads for the LEDs? I have one where the power led returns to +5, but the hard disk LED returns to +3.3--and one that uses a two-color LED, so the direction of current flow can change.
 
That would be correct. In your instance the white wires are being used as the negative lead with the colored wire indicating the positive.
 
Chuck(G) said:
I don't think I've ever seen an indicator LED on a case assembly go bad, much less three of them. Are you certain that this is the problem?

Aren't most motherboards set up for individual leads for the LEDs? I have one where the power led returns to +5, but the hard disk LED returns to +3.3--and one that uses a two-color LED, so the direction of current flow can change.
Click to expand...

There are numerous failure modes of LEDs:

https://en.wikipedia.org/wiki/List_of_LED_failure_modes

I come across dead indicator LEDs all the time, especially on 25+ year old machines. The most common failure is that the LED was plugged in backwards for an extended period of time and fried. Other failure modes I've seen were the current limiting resistor (where 3v LEDs were used) going off and passing full current to the LED and destroying it. Old LEDs also just fail naturally.

OP, if you're replacing the LEDs, make sure they're either rated for 5 volts, or use a 100 ohm resistor in series if you're using a more standard 3v LED.
 
Chuck(G) said:
I don't think I've ever seen an indicator LED on a case assembly go bad, much less three of them. Are you certain that this is the problem?

Aren't most motherboards set up for individual leads for the LEDs? I have one where the power led returns to +5, but the hard disk LED returns to +3.3--and one that uses a two-color LED, so the direction of current flow can change.
Click to expand...

Yeah, I am sure...none of them worked when the motherboard was hooked up...I tested one of the new ones on the wire and it lit up fine....so the originals are either really really dull or completely blown...

NeXT said:
That would be correct. In your instance the white wires are being used as the negative lead with the colored wire indicating the positive.
Click to expand...

Confused, maybe a typo, but you said the white is negative and the color is positive? I orignally said that I thought the white was positive and the color negative, but you also said I was correct? Just want to verify!!
 
It really doesn't matter since you can flip the plug around on the motherboard side if you get it backwards. But typically the common color (in this case white) is ground.
 
You're not going to hurt an LED by reversing it. As a matter of fact, the "bi-color" 2-lead LEDs are just two differently-colored LEDs wired in parallel, in opposing polarity.
 
FWIW, I've had cases where the colored wire was ground, the white wire was ground, or there was a mix on the same wiring harness. Sometimes there are + and - marks on the connectors themselves, I don't think I've ever had a case where the marks were wrong.
 
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