[kennedy]

I have an Apple 17" LCD on my Dual 500 G4 Power Mac. Its been working fine for years.

Today the screen is really, really dark... thought it was completely off at first. You can faintly see the screen. I shutdown and then powered up the machine... I checked the connections... any other ideas? Did my video card burn up? Or my LCD monitor die? Or?

Is there a monitor reset?

Thanks.

[davidflas]

Could be that your backlight burned out, that would explain why you can hardly see the display. Do you have any other video cards or another mac to test this out? Hope that helps.

[kennedy]

Originally posted by davidflas:
Could be that your backlight burned out, that would explain why you can hardly see the display. Do you have any other video cards or another mac to test this out? Hope that helps.

I have an iMac and a PowerBook 12... nothing that will drive the Apple display. Hmmm... I do have another PowerMac at work.

Is there a way for a user to replace the backlight? Or is that a service item?


Thanks!

[KeilwerthSX90R]

Is your power light flashing? That would indicate a backlight problem.

Josh

[kennedy]

Originally posted by KeilwerthSX90R:
Is your power light flashing? That would indicate a backlight problem.

No, nothing's flashing.

[bgordon]

Not to sound *too* obvious, but can you check the brightness setting on the Display preferences pane to see if it somehow got set too low? Reason I ask is because I tried to dim the display on my new PB 15.2", and the dimmest setting actually blacks out the screen to the point where you can *barely* see it. I know, apple and oranges, but maybe this might be of some help.

[kennedy]

Originally posted by bgordon:
Not to sound *too* obvious, but can you check the brightness setting on the Display preferences pane to see if it somehow got set too low?

Double-checked. I slid it around to no effect.

The loss of backlight seems to make sense... though I do still have the lights under the power and brightness controls on the display. Are those related? I would think they were wholly separate.

[kindbud]

I *think* there is more than one backlight. Typically, a burnt-out backlight will result in a dark section of screen...the top or bottom, for example. To lose more than one backlight at the same instant seems unlikely. Perhaps the entire backlight stops functioning (by design, maybe) if one tube blows. Hard to say. If owners of similar flatpanels had just one tube blown and a dark section of screen - I'd know for sure for what happens when a tube blows in that particular monitor.

I'm not 100% certain, but I'd suggest that the 'inverter' circuit is bad. The 'cold cathode' light tubes require high voltage for operation and this voltage is provided by a power supply commonly called an 'inverter'. Sorta like a flourescent light needs a 'ballast' to operate.

For MOST flatpanel displays, the 'inverter' circuit board is usually available as a replacement part. The same is true of the ccd (cold cathode) backlight assembly. The backlight is one unit that contains several light tubes. Even if one tube is burnt, you must replace them all by replacing the entire assembly.

Again, I could be totally wrong in my diagnosis. Don't run out and buy an inverter board just because I think that's what's wrong. BUT...if you want to avoid the high cost of an out-of-warranty-repair I suppose you could find replacements for the inverter and backlight by simply looking at the manufacturer and model# of the flatpanel. Apple doesn't manufacture flatpanel LCDs, they only make the plastic shell. You probably can't buy the inverter and backlight directly from Apple anyway - not without their technicians installing it.

If I were you, I would disassemble the monitor and check the inverter board (high voltage, don't touch anything on it) for obvious burnt components or raised/burnt traces on the circuit board. (The inverter board will usually have 2 rather hevily insulated (high voltage) wires that connect to the backlight.) Smell it. It shouldn't have an acrid odor. Check the wiring connections, too, it could be a simple thing like that causing your problem.

If the inverter 'looks bad', then replace it. Chances are extremely good that it's the faulty component. If it looks OK, then you have a dilemma. In my opinion, the odds are pretty even that the culprit could be either the backlight OR the inverter. Your odds are near 100% that it's one or the other.

Check the prices on the replacement parts. Try not to purchase them from Apple (big $). The parts may be Apple-specific which pretty much means you have to get them from Apple. The shape of the monitor's shell, for example, could have required a specially-shaped backlight or inverter.
I'd buy the inverter first, cross my fingers and hope that the CCD backlight assembly really does last about 10,000 hours on average...and it's not likely to be dead.

Go with your heart, grasshopper.

[atFault]

My 17" Apple LCD lost a backlight and it sounds similar to your problem. However, I only lost the top half of the display as there is at least 2 backlights in this model. This was accompanied by the power switch light pulsating the backlighting problem code continuously. My understanding is that the error code is for backlights and not necessarily the circuits that power them.

From the current information, I would agree that the problem does not appear to be the backlights, but something underlying.

Be sure to check the basics first, by trying it on a different machine, as the brightness must be controlled somewhat by software and it would be terrible to tear the display apart and have it be a corrupt preference for some reason. I have never heard of a problem like this and I am speculating somewhat, but brightness is controllable in System Preferences so it could be possible.(?) If anyone knows different, please correct me.

Good luck,

atFault