jimeney Posted October 22, 2007 Share Posted October 22, 2007 Hi Everyone, I'm hoping for some help with my intel iMac which no longer wants to boot. The lead up to this was as follows: 1. Sound went stuttery and computer became unresponsive (presuming due to high CPU usage, cause unknown). 2. Had to hold in power button for 10 secs to force a power down. Â Since this, the computer will not boot, fans and harddrive will spin up when power first comes on, but no chime, no picture on the screen and the light on the front stays lit. Short of taking it to an Apple shop do you have any suggestions? Â I have been to the apple website and tried all the options on their support pages. - remove power cable, leave out for 30 seconds, try powering up (resets SMC) - CMD + OPT + P + R (does nothing, presume this only works when the apple logo is showing). Link to comment Share on other sites More sharing options...
mifki Posted October 22, 2007 Share Posted October 22, 2007 remove power cable and re-insert while holding the power button Link to comment Share on other sites More sharing options...
jimeney Posted October 22, 2007 Author Share Posted October 22, 2007 thanks for this advice, what does this do? Link to comment Share on other sites More sharing options...
mifki Posted October 22, 2007 Share Posted October 22, 2007 dunno . (thats the proper way to reset the imac), apples site doesnt say holding power button re-insert the cable. But its the only way i ever got my imac working again. Link to comment Share on other sites More sharing options...
U.C. Posted October 22, 2007 Share Posted October 22, 2007 You shld try that. When I do that my iMac fans spin up really fast. I think it totally resets the SMC. Link to comment Share on other sites More sharing options...
jimeney Posted October 22, 2007 Author Share Posted October 22, 2007 This hasnt worked I'm afraid the smc has been reset though as the fans are spinning full speed continuously, however nothing else has happened after this. No picture, no chime. The light on the front has not come on at all. Will have to pull the plug to stop it. Any ideas? Link to comment Share on other sites More sharing options...
Lactobacillus P Posted October 22, 2007 Share Posted October 22, 2007 This hasnt worked I'm afraid the smc has been reset though as the fans are spinning full speed continuously, however nothing else has happened after this. No picture, no chime. The light on the front has not come on at all. Will have to pull the plug to stop it. Any ideas? Â Take it back to the Apple Store Link to comment Share on other sites More sharing options...
Darkmatter Posted October 22, 2007 Share Posted October 22, 2007 maybe it's your hard drive. Link to comment Share on other sites More sharing options...
jimeney Posted October 22, 2007 Author Share Posted October 22, 2007 is there a surefire way of diagnosing this fault? would a faulty hard drive stop the imac from getting to the apple logo (i thought this was in firmware rather than on the HDD). Cant take it back as its over a year old, bought it used and no warranty what now??? Link to comment Share on other sites More sharing options...
Numberzz Posted October 22, 2007 Share Posted October 22, 2007 If you have the Install Disks, insert them, and when the iMac is turning on, press and Hold the "c" key. If that works can you say so? Link to comment Share on other sites More sharing options...
jimeney Posted October 22, 2007 Author Share Posted October 22, 2007 the imac takes the disc which suggests this is not a power issue as the drive has power. The drive spins up as though its trying to do something and then nothing, the same as before, no chime, no picture, just the light on the front on. How do I get the disc out?!?! Link to comment Share on other sites More sharing options...
mifki Posted October 22, 2007 Share Posted October 22, 2007 Just take it to an apple store, its pretty {censored}ed up Link to comment Share on other sites More sharing options...
Lactobacillus P Posted October 22, 2007 Share Posted October 22, 2007 Just take it to an apple store, its pretty {censored}ed up  Yeah, getting it fixed probably won't cost as much as getting a new one Good luck! Link to comment Share on other sites More sharing options...
jimeney Posted October 27, 2007 Author Share Posted October 27, 2007 OK today I bit the bullet and opened the iMac up. I replaced the PRAM battery and reseated all the cables - still no change which means it must be the logic board (if it were the power supply, would I get as far as I am with the boot process - fans spinning up, lights coming on etc?). So the next question is how much will it cost to get my logic board replaced (no way I'm gonna attempt doing that)? I will likely sell it as faulty or strip down and sell the parts if its more than £300 to get fixed. Link to comment Share on other sites More sharing options...
Darkmatter Posted October 27, 2007 Share Posted October 27, 2007 hi jimeney, have you tried this? No Video, No Boot Chime, White LED ON (Symptom 1) The iMac will turn on (indicated by the front LED ON), but there is NO boot chime and No Video on the display. The faint sound of the fans, hard drive, and optical drive may also be heard. Reset the SMC (Formerly SMU). Turn off the computer by choosing Shut Down from the Apple menu, or by holding the power button until the computer turns off. Unplug all cables from the computer, including the power cord. Wait 15 seconds. Plug in the power cord while simultaneously pressing and holding the power button on the back of the computer. Let go of the power button. Press the power button once more to start up your iMac. Does the computer display video after successfully resetting the SMC? Yes: Problem solved. No: Continue to next step. 2. Verify that only supported SDRAM memory has been installed and that it has been installed correctly. Unsupported and/or defective memory can prevent the iMac from booting. It may be necessary to install known good memory for testing purposes and replace any unsupported or defective SO-DIMM's identified during this process. Does the computer display video after verifying and/or replacing the memory with known good memory? Yes: Problem solved. Verify full system functionality before return the system to the customer. No: Replace the logic board. No Video, Boot Chime heard, White LED ON (Symptom 2) The iMac will turn on, the boot chime can be heard, a white LED appears on the front bezel and sounds from the fan or drive activity can be heard, but the display has no picture or color. 1. Check if the computer is sleeping. Press the space bar to wake the computer from sleep mode. Did the computer wake from sleep? Yes: Put the computer to sleep from the Apple menu and wake the computer again to test. Check Energy Saver setting to see when the computer has been designated to sleep. No: Continue to next step. 2. Reset your computer's PRAM (Parameter RAM): If your iMac is on, turn it off by holding the power button until the unit powers off. You should hear the fans go quiet. While the computer is off, with your left hand, hold down the Apple key, the Option key next to it, and the letter "R" key on the keyboard. When you have these keys all pressed down, push the power button with your right hand and then quickly move that hand to hold down the letter "P" on the keyboard. Keep these four keys pressed while the computer starts up. Make sure you hold down the four keys (P - R - Apple - Option) while the computer is starting up. When you hear the computer's start up chime for the second time, you can let go of the keys on the keyboard. If you didn't hear at least two startup chimes, go to the top of this section and begin again. It's important that you hear two startup chimes when performing this procedure. This indicates that you have successfully reset the computer's PRAM (Parameter RAM). 3. Does the computer display video after successfully resetting the computer's PRAM? Yes: Restart the computer from the Apple menu and make sure the computer is now working correctly. No: Continue to next step. 4. Make sure the machine is powered off; power off the machine by holding in the Power Button on the rear of the machine. Turn on the machine. Observe the white LED on the front bezel during startup; it should go out after a few moments. Did the LED go off? Yes: If the LED went off, this indicates that the main logic board has communicated with the LCD display for video signal and your main logic board should be good. You can confirm by connecting an external monitor and checking to see that you have video out. Go to Step 8. No: Continue with the next step to reset system power management (SMC). 5. Reset the SMC (Formerly SMU). Turn off the computer by choosing Shut Down from the Apple menu, or by holding the power button until the computer turns off. Unplug all cables from the computer, including the power cord. Wait 15 seconds. Plug in the power cord while simultaneously pressing and holding the power button on the back of the computer. Let go of the power button. Press the power button once more to start up your iMac. Does the computer display video after successfully resetting the SMC? Yes: Press and hold the power button until the computer powers off. Start the computer again and confirm that front LED is reliably going off. If the computer still has no video but the LED is reliably going off, continue with step 8. No: Go to the next step. 6. Unplug the iMac and remove the SDRAM. Replace with known good SDRAM. Plug the iMac back in and power the unit on. Does the front LED go off after a few moments now? Yes: Replace the original SDRAM and test again. If the front LED does not go off with the only the original SDRAM installed, replace the SDRAM. If the LED is now reliably going off after a few moments, but yet you still do not have any video, go to step 8. No: If the LED remained on, the main logic board is not communicating with the LCD panel to generate video. Replace the main logic board. 7. With the LED going off, you may have a No Backlight condition or an LCD failure. In a dim room, turn the display at an angle to you and look closely at the display. Is the display completely black or can you see a dim, purplish light or glow to the display? Completely black: Replace the inverter Dim purplish light or glow: Replace the LCD panel. Link to comment Share on other sites More sharing options...
Roy Jovero Posted October 27, 2007 Share Posted October 27, 2007 Maybe your RAM went bad somehow? Same thing happened to my old G3. I just replaced the RAM and it worked again. Link to comment Share on other sites More sharing options...
jimeney Posted October 28, 2007 Author Share Posted October 28, 2007 I've read the same service manual and tried all of the above. Also replaced ram with known good from my macbook, and the original factory installed ram before it was upgraded to 2gb and neither make a difference. Thanks for your advice and tips though! Link to comment Share on other sites More sharing options...
Darkmatter Posted October 28, 2007 Share Posted October 28, 2007 If that's the case, then your logic board is defective as you already mentioned. and im positive about that. You need to ask apple how much will it cost you to replace the logic board of your iMac. Link to comment Share on other sites More sharing options...
jimeney Posted October 28, 2007 Author Share Posted October 28, 2007 thanks for confirming what I kind guessed to be the case. As an update to this, I turned on my intel macbook today and guess what . . . same symptoms, on this machine however the picture became garbled before the macbook decided to die, talk about bad luck eh I'm thinking perhaps a power issue could be the case as both machines are in the same household, although different plug sockets. Do you think a voltage spike / surge could zap the logic board? Link to comment Share on other sites More sharing options...
A Nonny Moose Posted October 29, 2007 Share Posted October 29, 2007 If its under warranty, take it in to get it fixed. Seriously, I saved a ton by taking my iMac G3. Link to comment Share on other sites More sharing options...
jimeney Posted October 29, 2007 Author Share Posted October 29, 2007 no warranty on either machine Link to comment Share on other sites More sharing options...
Darkmatter Posted October 29, 2007 Share Posted October 29, 2007 most spikes are brief and low amplitude and the power supply of your macs can handle most of these to protect the logic board. your case is very rare. Link to comment Share on other sites More sharing options...
jimeney Posted October 30, 2007 Author Share Posted October 30, 2007 would this affect the macbook though, considering the power supply is a seperate unit? an update to the macbook saga is that it will now sometimes boot, and will crash out every now and then with the graphics becoming stuttered, and whatever sound being played will constantly loop until the power is pulled. Does this sound like a software issue? there is nothing in the system logs to suggest a kernel panic or any other such issue, and booting into the technical test on the os x cd suggests all hardware is ok. Link to comment Share on other sites More sharing options...
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