GUIDE: How to Test and Use an LCD's LED backlights

[phaZed]

Originally Posted by NYJimbo

I just want to note that I for one appreciate posts like yours, SO FEW members of this board post anything like this.

I was just thinking a schematic or something on how to make a LCD cable/power "thingy" would be better for the average tech to use on a daily basis.

Not trying to start some kind of ugly back and forth on your technique or anything. Props for your electronics knowledge.

No arguments needed, and I appreciate the feedback.

I suppose my point is... what is easier than having a Multimeter and a 3-inch piece of wire for fully testing an LED backlight? When I test a customers LED backlight I simply drop the LCD onto the keyboard and use a multimeter while the machine is on. No need to take off the LCD cable from the machine. We let the machine provide everything from the original cable.

Most of the time the contact pads are marked, so any half-way proficient tech should be able to touch each one with a test probe. The only thing your tech needs to know is that each one of these contact pads is NOT 0v.. not hard, quick, and effective.

If a contact point is 0v then with a single wire in-hand you can provide the needed voltage to said pad and turn on the light. If that works then you can test the cable and motherboard and see if the PWM and ENABLE signals exist there.
If the signal is observed on the MOBO but not the cable, then the cable is bad.
If there is no signal from the MOBO then there is no need to order a replacement LCD cable and make your customer wait.

I suppose the problem I have with the LED tester cable is this.. the LED's *virtually* never go bad.. but LCD cables and MOBO's do... so lets get a $22 cable to test the LEDs only? What's the point of that?