Chosen Solution
Hello, just purchased a late 2009 iMac A1311 EMC 2308 as project, it’s not the first iMac I repair for hobby, but it’s my first 2009 model. This iMac don’t turn on, no fans, no HD, but the first diagnostic LED in the logic board is on, so I suspect can be the PSU or the logic board the culprint, but I want to be sure, because if I change the PSU and the faulty one is the logic board or viceversa, the fix will cost more than the actual value of a working iMac of same model beause I have to change some parts like LCD cables. I fixed on the cheap before some faulty iMac PSUs changing the capacitors, but no swollen tops on this one, so MAYBE is the logic board the defective one. I followed this guides, with no success Wont turn on. Bad PSU? How to Troubleshoot Logic Board PSU Issues Testing Troubleshooting.. As far I done the folowing: Reset the SMCChecked the button battery on logic boardChecked the voltages on PSUChecked the voltages on logic board I got some weird values, so I want to know if someone know the correct voltages for the PSU and logic board power pins. I have this values on a spreadshet, hope someone can help me to figure out whats wrong with these values.
Update (06/15/2018) @oldturkey03 thanks for your answer, I already had measured ther logic board test points, and that is what had me confused, if you look at the values I obtained, no all where what you read on the manuals, but now that I saw again the image you uploaded, realized that I was measuring the pins in the wrong order. Measuring again in the right pins, the voltages are more coherent, I can be sure about the logic board is faulty
@satoslp I’d start of by measuring on the logic board test points.
Pin 4 will have to have 12 Volt if your power supply is good. If it does not then you most likely have a bad PSU Locate diagnostic LEDs in bottom case vents. Plug AC cord into system. Verify if diagnostic LED #1 turns ON. You may alternately check for presence of a 12V DC signal between pin 4 and pin 1 of logic board. Yes Standby power voltage being supplied by power supply. No Replace power supply.
Hi guys, if have also a 2009 iMac A1311 EMC 2308. Its not powering up. diagnose led 1 is on12V on pin 4 is presentafter pressing power button, 12V is present on pin 11 but diagnose led 2 stays off!power on request signal (pin 12) has 0V after pressing the button, arround 4V before pressing it In the manual it says its probably the PSU. But I thought the power on request signal comes from the logic board?! Does anybody has an idea? Thx in advance! Greetings from germany, Ruben
