iMac G4 20" flatpanel display issue
 

I have a customer who's iMac doesn't display and I just wanted to bouch the steps I've tried up to now to see if I missed anything before sending it in for repairs.

So Symptoms:

The computer does turn on, you can hear the hd going at it, you hear the chime and all, but the screen lights up a bit (you can see a light halo around the side) and stays black.

What I've done:

1. Was able to boot from another monitor and from another Machine in TDM
2. Reset PRAM
3. Reset PMU
4. Logs are not showing up any issue at boot time
(can't do OF steps of any kind since I have no display)

My diagnostic:

Since I can see that the display does power on, I'd think the issue is either with the connector on the logic board
or the cable going from it through the arm to the display itself more than the LCD itself. Any one have another opinion or ideas ?

can you actually see the display? Is it just the backlight that went out? If so, more than likely it is your inverter board that went bad.

If the screen has a burned out look (like the back light actually went dead) you would have to repalce the screen since it is all one piece on those.

can you boot up with video out from the video out port adapter on the bottom back? Reset NVRAM that way with an extra monitor hooked up.

It could be the arm, but more than likely since no errors are coming up I am going to say it would be the inverter (most likely) or the screen (less likely) since the OS does not log any kind of failure with that hardware. The arm harness is all one piece and it is spring loaded, so if there was a cable chaffing or something of the like I would think you could feel it snag or here some sort of crunch noise from it.

What I can see if the light is low is a halo of light around on the edges of the screen.
I'll try with an extra monitor to reset NVRAM. (I know that works)

When I move the arm it moves as smoothly as ever.

So if its the inverter, is that something that I could fix "in house" or it has to be sent to Apple ?

is it under warranty?

The inverter is fairly easy to replace IMO, since it sits on the side of the screen. I think if you are comfortable taking apart computers this should be no huge task for you. I will warn you that even though it is not hard, getting the bezel back on all the way can be annoying (taken me up to 20 minutes before to line it up straight so it will snap down in place).

if you have another imac you could easily swap one out. You take out the three screws on the bottom of the screen and lifte the screen up and towards yourseflf to pop it out. The inverter board with be the small little piece on the side with two cables, one on each end. Each cable is like pink and blue and has a pair going into a white snap connector. That little piece is the one to replace, and it will tell you if its the inverter or the backlight itself.

PM me your email if you need any further help, also drop me the serial number of the imac.

Not under warranty any more, so I'd be more inclined to try to do the repairs myself (I've been taking apart computers for the last 5 years so I hope I know what I'm doing :D). Sadly I don't have a second iMac to try with. Where could I get an inverter then ?

apple, or aasp, they retail for like 25 to 30 dollars i think, if you shoot me the s/n i can look it up

ah okay i saw you sent me the PM

Update

The inverter board replacement did not work sadly. I'm going to look into removing the screen from its arm so it doesn't take up space and then use the mini-vga adpter to use an external monitor. Much cheaper than a replacement (1000$ CAN before taxes and labour !).

I've just been afflicted with this very problem. It's worrying me as I'm a graphic designer who's not that technically clued-up and fear that a solution is going to cost me a fortune.

If anyone has any further advances or information please let me know. Thanks.

basically this is how you troubleshoot it.

verify video out from the logic board works - check

reset firmware, pmu, nvram, pram, etc - check

if problem still persists you replace the inverter board

the inverter board is the cheapest part, and one of the most likely to fail. If the inverter board does not fix it, then you know its something else (screen, logic board, the neck, or some video/power cable).

Cheers.

I'm now told by the local Apple Centre that it's the logic board gone. Gonna cost me £500 to put right after paying £1750 only 2 years ago for it! I'm devastated.

At least its not the screen that went south... Then you'd find that the logic board replacement is cheap.

Raven, were you able to rescue the iMac G4
 

I have an identical machine - lower half of display is dark, upper half (usually) OK, and I'm hoping to use my software by making it into a "round mini) with an external screen and removing the chrome arm and (sigh) lovely 20" screen.

If you know how, could you share?

There is a video out port on the back of the G4 iMac with VGA out. You can hook that into an analog monitor with that video out adapter no problem. However, if its a back light issue you would only need to replace the inverter board to fix it most likely, which is not a super expensive part.

The cable (hard to find in Singapore) works fine, but.........
 

The Apple mini-VGA to VGA cable hooks up to an external monitor, and aside from an annoying delay, this works fine. Now, I hope to remove the large and apparently useless 20" display and its arm, and end up with a nice semisphere. Ideally, I could then swap the connectors on the video out so that the primary display is connected to the mini-VGA out port, for faster display. Unfortunately, can't find directions (searched Apple, Googled, etc) on how to do these tasks.

Ideas? URLs? Diagrams? Pictures?

Thanks in advance,
Lee

I have a 15" G4 iMac with the same problem – HD spins up and screen starts to light up but doesn't finish; you can faintly see the desktop. I put my computer to sleep overnight and it usually happens when I go to wake it up, although on a couple of occasions I have restarted and the screen remained dark. I put it back to sleep using Option-Command-Eject, which may take up to 15-20 seconds, and try waking it up again. Sometimes it takes 5-6 tries to wake up. I had both the logic board and inverter board replaced under AppleCare, to no avail. Of course, when it was in the shop it wouldn't so this. I've tried every suggested fix, including reinstalling Tiger and using no third-party software, with no success. The problem is getting more frequent.
My technical understanding of computers is limited, but with the talk of LEDs for lighting the screens, it was mentioned that they presently use fluorescents. This problem reminds me of a fluorescent tube that starts to light up but doesn't finish; there's just a little glow at the ends. I don't see how this could be fixed. So it's either an external monitor or a new computer.
Cheers, Peter

I'll try this again - previous posts havent posted! >(

How long is the lag with the mini-VGA adapter?

I have the same screen problem. I believe the screen is fine since the backlight comes on when power is on, just nothing displayed. I believe it to be a GPU problem on the logic board.
I found a thread where someone fixed this problem on an IBook. Does anyone know of a solution for this problem on this system? (Mac Engineers give your views)

Hey guys n gals, having the same prob myself, screen is blank, but seems to be working as the backlight is working, just no display. I'v enarrowed it down to a GPU problem through hours of searching the web.

How much of a lag is there with the mini-VGA adapter? Is it really bad when using the mouse? :eek:

Also does anyone know of any techheads who have attempted and fixed the GPU problem on the logic board? If so can you put me in touch with them as i sorely want to fix this once and for all. There was a problem with the solder on the ibook GPU's coming loose and i found a thread once whereby someone fixed this by using a small tealight holder on the GPu and lots of some flammable substance. I wouldnt even conside this with my system, but wondered if there were any other solutions? (MAC WORKSHOP GUYS IN PARTICULAR!!) :D

No the video out should display like any normal monitor does there is no delay.

Hello all... this is my first post on these forums which I happened across while Googling the very issue that is discussed in this thread...well, almost the same issue, the only difference being that I am having this problem with my recently purchased iMac 24".

Rather than send you to the top of the thread to remind yourselves of the original issue posted here, I quote it now:

"The computer does turn on, you can hear the hd going at it, you hear the chime and all, but the screen lights up a bit (you can see a light halo around the side) and stays black."

After contacting the Mac help line (phone) we determined that the problem could relate to files in the Startup files area ( I had not long ago installed Parallels Desktop and there were two related startup files installed - although I would have thought a startup file issue would only rear its ugly head after the OS had loaded). As a result I removed the files from the startup folder and low and behold, my iMac started to boot every time with the display working perfectly! Now however, after a week or so of being well behaved, it has suddenly decided to experience the same problem again - I have checked for startup files and nothing is in there.

Basically, I get the chime, the screen lights up ever so slightly (but is still almost black) and I know it actually boots the OS and enters the desktop view as I get certain responses from hitting keys (blips when I hit the volume key etc). If I switch off the power at the mains and switch back on and press the power button enough times, it will eventually start with the display working as it should... but that can mean powering up and powering down as much as 10 times!! At least this eliminates the possibility that the LCD is completely dead and I suppose points to a possible driver or graphics card issue. It also means that I can at least continue to work on the thing, even if I am likely to get a repetitive strain injury from starting it rather than using it :)

Any thoughts or anyone else with this experience with an iMac who may have resolved the issue?

Grrrr!!!! :mad:
just bought the mini VGA to VGA cable to use with my p.c's 21" monitor (dell ultrascan) I plugged it in expecting the best and this is what happened.

System off - flashing monitor light (no display)

push button to power on - chimes and flashing monitor light (still no display)

hard disk whirrs - flashing light goes off (for 2 seconds) then flashes again (still no display)

backlight comes on with mac monitor (still no display)

then the backlight flicks off for a second, then flicks on again (still no display)

and thats where it gets to

could a problem with the hard disk be causing this does anyone know?
im getting verrrrry frustrated!!! :mad:

A bad hard disk would not cause the video not to work. It may be the video it self but if you get nothing on an external display then the problem could be video related. Make sure its hooked up then power it on and see if that works because if it gets the chime then it is passing POST.

By video problem i take it you mean the chip on the logic board? the GPU?
Would a problem with the GPU chip affect the mini-VGA out slot as well?

Nope it would mean you have to replace the whole logic board since everything is integrated into one piece.

ack! looks like a fond farewell to my mac then and a quick call to the old insurance company! thanks for the help anyway.

My iMac screen is completely black, can’t even see the desktop with any light source shined at the monitor. Would it be safe to assume that the lcd display burned out, or should I check to see if there’s any connectors that might be messed up... or purchase an inverter?

My screen is totally black on my iMac... There’s power going to the screen, but no image whatsoever.

Hook it up to an external monitor, if it works then your back light is not working and it is probably the inverter board (cheap fix) if the external display does not work then its probably the video chipset (expensive fix). that will help you narrow it down.

how do you differentiate between an inverter being bad and a blown fuse on the logic board or corroded wires for that matter? I figured that with a blown inverter the screen would be black but you could barely make out the video being displayed, not a completely black screen.

Ack me too!!
 

I've got an iMac G-4 20" Flat panel too.
It's got a very dim blue screen, can't see any detail, but computer starts up fine, seems to ready to go to work, responsive to the mouse.
I am guessing it's the inverter board, but don't have a spare monitor to try on it (much less the VGA connector). Have done the pram/ software checks to no avail. Is there any other way to check this out.
Also, I cannot get anyone to confirm the inverter board part #, Can anyone help?
This site says it has it with the # 922-6129 : http://www.macsupportstore.com/ but when I take it a part, this number does not appear on the board. Do I have a good #?
thanks

The actual part often don't show Apple's part number, but 922-6129 is the correct inverter.
You really should verify that the video is good on the logic board by trying an external display. The adapter is exactly the same as those that shipped with any iBook, if that will help you locate one.
If an external display also does not work, then you have other (more expensive!) problems, probably a logic board. Good external video, then the inverter is a good guess. Without trying that external video, then you just have a shot in the dark (so to speak!)

A blown capacitor on the logic board will be bloated and often oxidized. So physically checking the caps will let you know.

A bad inverter board just takes out the back light, so the display still works. Shining a lamp on it or a flash light to see the desktop or hooking up an external monitor will show you that the video still works.

Does anyone have any links to schematics for the logic boards on these imacs. It seems to be a common problem with the video chip on the logic board failing. I remember seeing a post about a company that fixes this problem but alas I did not bookmark it. I think you send in the logic board , they test it then see what it is going to cost you. I seem to recall about $600 average being quoted for this service.
Stewie

Help
Can't seem to find it!!
iMac G4 20" Flatpanel inverter board p/n 922-6129
Tried:
Welovemacs.com
DT & T Computer Services
PinnacleMicro Optical Storage
TheMacSupport Store

They all list this in their catalogs, and some show stock, but they have canceled their orders for lack of stock.

Can anyone please give a lead on where one might find one? Thanks

Try BlueRaven - http://www.blueraven.com/us/Service-...OEPartNo=11133

Thanks DeltaMac, but they seem to be out of stock also. Any other suggestions??

Any local AASP can directly order the part from Apple and you can buy it direct.

DeltaMac, cancel my last request-BlueRaven had it after all. Thanks again

My 17-inch flat panel Apple iMac display just stopped working. The screen appears black but you can see the windows faintly in the background after the machine boots up.

I did some research and found that Apple has had an inverter assembly problem in the past. There is a class action recently settled on this matter regarding the Apple Studio Displays. Other Apple computer owner display complaints continue.

After taking my computer in to the "genius" bar, I was told that the problem was most likely the inverter assembly. I was quoted a cost of $39 for the part and $135 for the labor. Just today, I got a call from the Apple Store and the techician said that the problem is not the inverter but the LCD panel itself. The news was that this part was $389! With the addition of the labor, this repair would be over $500!!

Is the LCD replacement something a novice can or should attempt? Is this repair ludicrous on a machine that is four years old? Is the only option attaching a different monitor to the system? This is unfortunate considering the display is what MADE this computer!

Clearly from my research, Apple has some "display issues" that are yet to be resolved. I'd like to know if there are other iMac who have well-cared for and conservatively-used Apple computers with this display problem. Please report your iMac display problem here;-)

Any wisdom from the more technically-expert readers would be most appreciated! I would like to make a consumer suggestion: notify Apple in formal, certified letter so that there is a record of the complaint. Otherwise, we, the owners may be the ones left covering the widespread problems.

iMacowner, it is most definitely a common problem that is mostly the inverter board - a relatively cheap part to obtain. If you have any basic fixit skills ,you can do it yourself and save a lot of money.Check first as the other posts say that you do not have logic board issues . If you plug in another monitor to the VGA port via a cheap $15 adapter and it works then your logic board as well as the included graphics chip is working and it will 99% be the inverter board. If you don't get anything on the external monitor then it is either the logic board or graphics chip that's at fault which ain't cheap to fix!
Stewie

Dim Screen
 

I too have a 17" Flat Panel G4 with a recurring "won't wake from sleep" issue. As mentioned above, the screen is black but with a barely visible desktop. Tried the usual fixes. PRAM reset. System reinstall. Random success that did not last.

Found the below Apple fix of resetting the PMU. Worked for me.

I Quote Apple— In rare occasions the settings in the Power Manager may become unusable, which can result in operational anomalies with the computer. For example, your computer might not turn on, not wake from sleep, or do (or not do) other things.

http://docs.info.apple.com/article.html?artnum=95165