Identify and repair/replace faulting component in LCD monitor

At present, I have 4 dead or dying-to-the-point-of-being-useless LCD monitors that I'd like to diagnose and fix.

They're all 28" 1920x1200 monitors, of various ages. I seem to go through one every 2 or 3 years, so the oldest one is about 8 years old, but has been sitting in a closet for 5 or so years gathering dust after it broke, and like that there. The newest one died several hours back. (And if that's not enough, I've got a few dozen similarly "worn out" ~19" screens to haul off to recycling for a client by next Friday, so it seems like this would be a highly worthwhile thing to figure out, and soon.)

They've all died from age, not being dropped or getting wet, and the symptoms are different in each case. (Which I can provide if that's helpful or there's no tool or general process to diagnosing a monitor failure.)

Anyway, this is a little out of my area of expertise, so I figured I'd ask for help here. Does anyone know how to diagnose a faulting component on an LCD monitor, and/or what tools I'd buy to do so? Through Google, I've found a bunch of places I can go to order replacement components, once I figure out which ones are faulty, but nothing really useful on how to identify what parts I need.

I think I'm looking for advice on what to look at once I crack the cases open, or an electrical tester of some sort, or any diagnostic tests I can do, but, as I say, I'm not sure, and a little out of my depth. Can anyone here offer me some advice or a push in the right direction?

HopelessN00b

Posted 2012-09-20T06:43:07.223

Reputation: 1 869

Generally speaking, monitors aren't user-serviceable. How are they dying? Dead pixels, screen dimming? – tombull89 – 2012-09-20T07:57:49.287

@tombull89 Not turning on x1, dim screen x2, corrupt display x1. I guess I should add a thing or two to the question to maybe clarify what I'm talking about here... – HopelessN00b – 2012-09-20T11:18:31.843

"dim screen" (getting dimmer over time) is a common CCFL backlight failure mode -- they do actually wear out, especially if run at full brightness for a long period of time (years). Sometimes a new inverter helps, but often the only fix is a new CCFL (backlight lamp) - pain in the ass to replace. – voretaq7 – 2012-09-20T20:13:27.543

Answers

There's only 3 functional parts of a LCD monitor (more or less). The decoder/power board, the LCD itself, and the backlighting.

If a monitor is dim, especially if that dimness is on one side (top/bottom, left/right) it's probably a backlight burnt out. You can get replacements on eBay usually, and cheap. These are crazy easy to break when not installed, so be extremely careful.

If the monitor has lines through it, or something similar, it's probably the cable between the LCD and the decoder board. It might also be a bad LCD or decoder, but reseating the cable isn't going to hurt.

If it doesn't turn on at all, use a flashlight (shine at an angle an see if you can see what should be on the display). It might just be the backlighting completely burnt out, this could also be an inverter issue (which is usually integrated into the decoder board). If there's nothing on the screen at all, the decoder is almost certainly fried.

Usual warning: the Power Board (usually the one "main" board) has enough juice to kill under certain circumstances. Make sure everything is unplugged before starting, and even that's no guarantee.

Chris S

Posted 2012-09-20T06:43:07.223

Reputation: 5 907

The one that isn't turning on is probably a goner. The one with the "corrupt display" is probably a goner as well. Both point to logic board issues.

The two with the dim screens could be suffering from backlight or inverter failures. In my experience, if the screen get a reddish hue, it usually points to an inverter. If they just go dark, it's probably a backlight. You can get various backlight inverters online for relatively cheap, so it may be worth replacing that before you go buying a whole backlight.

MDMarra

Posted 2012-09-20T06:43:07.223

Reputation: 19 580