iMac G5 - No picture or video on start

If you have not already, be sure to try resetting PRAM

http://support.apple.com/kb/HT1379

and if that does not help, resetting SMU (power management)

http://support.apple.com/kb/HT1767

When you plug it back into power, if you are using a power strip of some type, try connecting it directly to a wall outlet by itself (at least initially). Start it up with nothing connected, except for the power cord, then (if there is improvement on the display) add only standard USB mouse and keyboard.

There may be a hardware testing tool on Mac OS X instalaltion disc that came with the iMac, but that would not be useful if your display is dead.

If the screen is completely dead (dark), that might be a problem with the LCD or the LCD's backlighting. The logic board may be OK. One thing you can try is starting up normally, then shining a bright light on the display. If the LCD is working, but the backlighting is not working, you may see something being displayed.

You can tell by looking at the capacitors if they are bad. They bludge.

Google: g5 capacitor replacement kit

http://jimwarholic.com/2008/07/how-to-repair-apple-imac-g5.php

http://thecapking.com/applg5.html

Robert

I'm no expert on this. I have not seen the problem with my own eyes. I know what I read on the internet.

According to you, it's not necessarily that logic board is at fault if LED 3 does not light on.

I do not know the meaning of LED 3 lite or non-lite.

I went through the hyperlinks you provided and it's quite risky.

I not sure what you are referencing. My worry would be trashing the logic board. You have to evaluate the effects on your personal safety.

I'd try the repair after consulting with my friend who has an Electrical Engineering degree.

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Someone may be able to identify the problem, if you took a close up of the capacitors. They look like very miniature beer cans.

"Additionally you may also go to any Apple Retail Store with a Genus Bar, and have the Apple folks take a look inside the G5 and look at the caps on the iMac logic board for you."

http://jimwarholic.com/2008/07/how-to-repair-apple-imac-g5.php

I referenced this article above.

Here is a link with pictures. The top of the "can" seems to pop.

http://en.wikipedia.org/wiki/Capacitor_plague

Here is a picture of G5 with the capacitors circled.

http://www.flickr.com/photos/30825931@N06/3038393309/

http://www.gcsdblogs.org/roodhouse/?p=2124

Note: Some g5 power supplies have the problem too.

http://schutt.org/blog/2011/10/the-capacitor-plague-strikes-again/

iSamy wrote:

Hi,

I have done all these actions but the screen remain dark.I'm pretty sure that the board is faullty because the LED 3 on the board does not light on even after resetting the PRAM and SMU...Just too bas for me.

I'm getting different meanings as to what LED 3 means. How many LED do you have?

http://support.apple.com/kb/HT2831

According to this page, LED 3 is only going to light when you have an airflow problem.

http://support.apple.com/kb/HT2652

Do you have a link to what these LEDs mean? I may have re-acted too quickly to site the capacitor problem.

RObert

step 10...

LED 3 turns on last, indicating that the logic board and LCD assembly have communicated, and that the LCD is ready to receive video.

It could be the LCD is not communicating.

Does LED 3 turn on? Yes. This means that your miplane is working correctly to produce video. Skip to step 12

Step 11 ...

No: If LED 3 is off, this means that your logic board needs to be replaced. Please schedule a service appointment with either an Apple Retail Store or an Apple Authorized Service Provider.

Apple is recommending you replace the logic board.

Have you looked at the capacitors some more? If they are the problem, you may see busted tops etc.

Robert