I have this IMac as a personal collection and started to notice that it was making a noice during daily use. So I decided to give its first ever maintenance.
Once everything is clean and reassembled, I power it on but there's no reaction. After a bit of teardowns and reassemblies I give up to Google the issue. From there I learned that there are 4 diagnostic LEDs marked LED501-504. With the screen disconnected, I get the first led with a solid on, Led 502 turns on, blinks a few times then turns off. This repeats until I pull the power cord. Now to make sure the machine is receiving the proper voltage, I check a few points ( I'll edit it in once I figure how to do this on a phone) from where the PSU connects to the motherboard. Pins 1-3 get the 12v and 4-6 go to ground as they should but every couple of minutes pins 1-3 go to ground which I figure is a short. In one of the of pins 1-3, I disconnect the PSU from the motherboard and the short disappears altogether on the motherboard. Time to check the PSU, I poke around a few capacitors and find a few of them are shorted.... Here are some pictures of the PSU unmarked if the phone let's me.....
Once everything is clean and reassembled, I power it on but there's no reaction. After a bit of teardowns and reassemblies I give up to Google the issue. From there I learned that there are 4 diagnostic LEDs marked LED501-504. With the screen disconnected, I get the first led with a solid on, Led 502 turns on, blinks a few times then turns off. This repeats until I pull the power cord. Now to make sure the machine is receiving the proper voltage, I check a few points ( I'll edit it in once I figure how to do this on a phone) from where the PSU connects to the motherboard. Pins 1-3 get the 12v and 4-6 go to ground as they should but every couple of minutes pins 1-3 go to ground which I figure is a short. In one of the of pins 1-3, I disconnect the PSU from the motherboard and the short disappears altogether on the motherboard. Time to check the PSU, I poke around a few capacitors and find a few of them are shorted.... Here are some pictures of the PSU unmarked if the phone let's me.....
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