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My iMac can’t be turned on, liked totally dead. I checked PSU, voltages are ok (pin4 12 vol). I have checked LEDs, LED1 on, but LED2 off.
By bypassing SMC (while pressing Power ON button plus plug in iMac power cable), I can manage to turn it on, fan running fast, but no startup chime sound, black display!
Wonder why no chime sound, due to bad logic board or battery? Thanks for sharing your suggestions/comments.
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I’m suspecting you have a failed GPU board iMac Intel 21.5" EMC 2389 GPU Card Replacement
这个答案有帮助吗？
Not sure about it. In fact I suspect if the malfunction may be caused by bad battery on board, it's rather difficult to remove it from logic board to measure its voltage. Wonder if it's possible to measure its voltage without removing it from logic board?
@David444 - It's a cheap coin type battery, I would just replace it if you feel that is the issue.
@danj definitely I will do it, but it's a bit complicated to remove all small cables, and finally get the battery out. Thanks
@danj I have changed the battery, unfortunately don't see any change, no chime, black screen. I am looking into ways for GPU card replacement/upgrade, especially this one: 2011 iMac GPU Upgrade at https://www.youtube.com/watch?v=0b_YzIjO...
Not sure if it can be used for 2010 iMac, also the process involves a lot of software hacking, rather complicated. Plus side is the nvidia k610m very cheap, us$14!
Other than getting the original Apple board you need to go through the process laid out in the Vid.
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Let's give this a try: Using a USB keyboard restart your system but this time press the T key to see if the system can enter into Target Disk Mode. If it does you should see a Firewire Icon on your screen do you?
Reference: Mac startup key combinations
由 Dan 完成的
@danj, Just did a test, unfortunately screen black, so the iMac can't enter the target mode, only signs I can tell: 1. LED#1 on, 2. Fan loud, nothing else. Thanks for your suggestion.
由 David444 完成的