You are talking about the iMac G3 CRT model? CRT's do not have back lights.
There was a problem with installing 10.2 or greater. You should check to verify that you have the correct level of firmware.
You did not say if the CR T work in the past or not. Did you get this machine you used?
Robert
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You need to figure out the level of your firmware before installing 10.2 or greater. ( The PC name for firmware is BIOS. ) Installing 10.2 with a down level firmware will most likely make your iMac unusable and difficult to fix.
Figuring out what level of firmware you have?
1) Mac OS 9.x or 8.x, you need to use the Apple System Profiler.
Apple -> Apple System Profiler
2) Mac OS X, use the System Profiler.
Apple -> About This Mac
click on the More Info... tab
click on Hardware
read the Boot ROM Version
3) Open Firmware, boot into Open Firmware.
Power on your iMac while holding down command
option+of
The first output line contains the firmware level. Mine reads:
Apple PowerMac4,1 4.1.9f1 BootRom built on 09/14/01 at 13.18.04
Copyright 1994-2001 Apple Computer Inc.
Some machine may not contain the firmware level but some other number which can be translated to the firmware level.
On my machine, I have 4.1.9f1.
What firmware do you need?
http://docs.info.apple.com/article.html?artnum=86117
For a slot loading iMac, this article indicates that you need to be running 9.1.
http://docs.info.apple.com/article.html?artnum=75130
"The iMac Firmware Update 4.1.9 will only run on iMac computers with lot-loading CD or DVD drives running Mac OS 9.1 or later from a local drive. If you are using Mac OS X you must boot from a local Mac OS 9.1 or later writeable partition (not a CD, or network disk) prior to following the update instructions."
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You installed Mac OS 10.2 or greater on an iMac G3 and you forgot to update the firmware. Now, your iMac won't display anything on the screen or the screen displays funny things. This occurs on the first boot after the installation. A few folks have reported other problems like difficulty in booting.
This PDF file that describes several procedures for loading the new firmware. This page is often cited in this forum and is probably the best around:
http://mrjcd.com/gileskennedy/iMacfirmware_problem_v12.pdf
Online copies of most of the pdf file:
http://www.avnr55.dsl.pipex.com/dotcom/panthereatsimac/problemsolver
http://www.capecodgraphics.com/imacfirmware.htm#II_Intro_toproblem
A detailed analysis of what caused the display problem and another solution involving holding down the Programmer's button:
http://www.capecodgraphics.com/pages/macintosh.html
Getting display screen under Mac OS 9:
http://www.macosxhints.com/article.php?story=20050218164736471
Another possible fix for dead-screen G3 iMacs
http://www.macosxhints.com/article.php?story=20050218164736471&mode=print
What firmware do you need?
http://docs.info.apple.com/article.html?artnum=86117
For iMac 333 MHz, iMac 266 MHz, & iMac 233 MHz, you need to use MAC OS 8.0.
http://docs.info.apple.com/article.html?artnum=60384
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Here are in some other commands that you can do in open firmware.
Hold down command-option-o-f then poweron your machine. Continue holding until the Open Firmware screen appears.
#In case you have a cd you don't want. How to eject a cd from the internal cd drive:
eject cd
#insert the cd
mac-boot
#You will need to quickly press the and hold down the c key.
In case you act too late, shutdown your machine. Hold down the option key. This will bring up the startup manager. Power on your machine. Click on the dvd image. Click on the arrow icon.
List of devices:
devalias
List of variables
printenv
This is a quote from the web:
Sometimes if volumes don't appear in Startup Manager (what you get when you hold down the Option key at startup), you need to reset the Mac's PRAM, NVRAM, and Open Firmware. Shut down the Mac, then power it up, and before the screen lights up, quickly hold down the Command, Option, P, and R keys, until the Mac has chimed twice more after the powerup chime. Then, before the screen lights up, hold down Command-Option-O-F until the Open Firmware screen appears. Then enter these lines, pressing Return after each one:
reset-nvram
set-defaults
reset-all
Why set nvram variable? I've had open-firmware based Pegasos PPC and it simply had boot command, so instead of:
setenv boot-device ud:3,\:tbxi
should be enough to write:
boot ud:3,\:tbxi
