intel imac with 10.4 Tiger crashes on boot

Hi,

The fact that you can't even boot from the original install disc leads me to believe there is a hardware issue. However, the fact that your computer passed the hardware test makes this confusing.

This is a long shot, but try unplugging all other devices besides the keyboard and mouse and see if anything changes. I've seen a computer power itself off before due to a faulty keyboard. So maybe even unplug the keyboard and mouse and see what happens. Also perhaps try leaving only the keyboard connected and booting up on the original install disc.

But I'm wondering if you have some faulty RAM, although I've never heard of RAM failing so absolutely that it prevents the computer from booting yet passes a hardware test.

 

How are you booting to hardware test?

Which hardware test are you running on the machine? Are you running AHT from the discs that came with it?

If you can boot from the AHT disc and run the test, you should be able to boot from the OS disc as well.

Try this:
First, reset the SMC on the unit by unplugging it completely, then clearing all power from the board (once unplugged, hold the power button down for about 15-30 seconds.)

Next, rest the PRAM (restart the computer while holding down command+option+P+R. Wait for at LEAST 3 chimes before letting go.

If your machine is not chiming, it is not passing the power on self test (or POST) If this is the case, look for any blinking coming from the power indicator light on the front of the unit. If it is flashing at all, your issue is most likely either failed RAM or MLB.

If the machine does chime but the symptoms persist, listen for any unusual noises (grinding, screeching, high fans, etc) as those would also be an indicator of a hardware failure.

Another way to try to boot from disc would be rather than holding the "c" key down (or "d", depending on the machine) while booting, try to hold down the option key instead to bring up the boot volume selector. Click on your install disc icon and hit the arrow to move forward and you should be able to boot to the installer and run the disk utility.

If those options fail to work, I suggest taking it to a service provider.

Any machine running 10.4 will most likely be pretty expensive to repair if it is a hardware issue, especially MLB failure.

Hope this helps.