I hate when this happens. I pulled my 20" iMac G5 with ALS out of storage recently and it works great except what I thought was overheating caused by old thermal paste. It would not overheat when fully mounted in its case but it would if I ran it with the back off. So, after cloning and installing a 2TB SSD system drive (it boots fast with and SSD and fresh install of 10.4 Tiger), I removed the MB tonight and repasted the CPU, GPU and whatever the third chip is on the back of the MB. I got disassembly instructions and kept track of all my cables and screws. BTW, this iMac has been no problem in all the time I've owned and used it except when the PS failed and I replaced it.
Upon reboot, the start up chime plays partially before LED 4 turns on red and shuts down the computer. What I've been able to figure out is LED 4 indicates an over heating condition even though the iMac has been on for about 5 seconds and is ice cold. I took it apart again and went through everything but upon reassembly it still does the same thing. I've tried a couple of SMD resets (there is no 2nd button under the power button contrary to pictures on the internet and OPtion-Command-P-R doesn't work because the iMac isn't on long enough for the key combo to register.
So here I am, with my hat in hand, asking for help. The usual answer is to replace all the caps, which I can do, but all the electrolytic caps look brand new with no caps doming and no leakage or fish smell on the MB. The damn MB looks brand new. But, I'm stuck and I hope someone has a suggestion. There appears to be a lot of confusion about how to reset the SMU but, so far, nothing makes any difference. I did pull the battery out but that made no difference, and since it's on for only a few seconds before it shuts down keyboard combinations don't seem practical. Also, Since this is an over temp situation, where does the iMac G5 measure the air temp to determine how hot the machine is?
I thank everyone for your thoughts and ideas about what's going on. I was afraid this would happen when I undertook this little project of breaking it rather than fixing it. I just wanted to help it stay cooler but instead I've broken it. Before, it worked even with the old paste but now adding new paste, it doesn't work at all. I'd hate to have to replace some 50 odd caps and that doesn't fix anything. i'd rather understand the issue just throw new caps and hope it fixes the problem.
Also, if necessary, where can i find good replacement parts, like a PS and MB if that's what it takes. This was my first Mac I owned so it has a special place for me.
Thank you all,
Gerry
Upon reboot, the start up chime plays partially before LED 4 turns on red and shuts down the computer. What I've been able to figure out is LED 4 indicates an over heating condition even though the iMac has been on for about 5 seconds and is ice cold. I took it apart again and went through everything but upon reassembly it still does the same thing. I've tried a couple of SMD resets (there is no 2nd button under the power button contrary to pictures on the internet and OPtion-Command-P-R doesn't work because the iMac isn't on long enough for the key combo to register.
So here I am, with my hat in hand, asking for help. The usual answer is to replace all the caps, which I can do, but all the electrolytic caps look brand new with no caps doming and no leakage or fish smell on the MB. The damn MB looks brand new. But, I'm stuck and I hope someone has a suggestion. There appears to be a lot of confusion about how to reset the SMU but, so far, nothing makes any difference. I did pull the battery out but that made no difference, and since it's on for only a few seconds before it shuts down keyboard combinations don't seem practical. Also, Since this is an over temp situation, where does the iMac G5 measure the air temp to determine how hot the machine is?
I thank everyone for your thoughts and ideas about what's going on. I was afraid this would happen when I undertook this little project of breaking it rather than fixing it. I just wanted to help it stay cooler but instead I've broken it. Before, it worked even with the old paste but now adding new paste, it doesn't work at all. I'd hate to have to replace some 50 odd caps and that doesn't fix anything. i'd rather understand the issue just throw new caps and hope it fixes the problem.
Also, if necessary, where can i find good replacement parts, like a PS and MB if that's what it takes. This was my first Mac I owned so it has a special place for me.
Thank you all,
Gerry
