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Good morning I’ve an iMac 21.5 mid 2010 A1311 EMC 2389 It boots only if I connect the cable while I keep pushed the power on button Then it starts up with fans at max speed Then I keep pushed the power button to turn off Then I push power button and it starts up with fans at max speed No chimes at all That’s the only thing I can do Also my Logic Board doesn’t have the SMC RESET button, is this “normal” ? On web I saw some logic boards with/without SMC RESET button. Here voltages Is there any other test to do ? Psu broken ? Logic Board broken ? Here diodes checked with multimeter on PSU, D3 should be blown, about D131 I really don’t know: D1 = 480 D2 = 470 D3 = 0 D31 = 620 D32 = 634 ZD39 = 640 ZD36 = 655 D39 = 536 D33 = 538 D131 = 560 (-) / 1665 (By the way LCD is NOT plugged and just LED 1 is ON and I have already the ATG) http://tim.id.au/laptops/apple/imac/imac… Best Regards
My psu Delta ADP-200DFB
Aggiorna (24/10/2020) Good morning, I’m a new user, is site offline or there’s just a long queue to get an answer ?
Given your symptoms I think you’ve proved your issue is not the power supply. I don’t generally dig into the logic board as it’s not documented and its difficult to test on its own. Instead, I rely on Apples diagnostic processes. So to start with here’s the Apple writeup on the onboard diagnostics: Here’s a breakdown of the onboard diagnostic LED’s: LED 1 - Indicates that the trickle voltage from the power supply is detected by the main logic board. This LED will remain ON while the iMac is connected to the AC power. The LED will remain on even when the computer has been shut down or put to sleep. The LED will turn off only if the AC power is disconnected or the power supply is faulty.LED 2 - Indicates that the main logic board has detected proper power from the power supply when the computer is turned on. This LED will be ON when the computer is turned on and the power supply is working correctly.LED 3 - Indicates that the computer and the video card are communicating. This LED will be ON when the computer is communicating properly with the video card. If LEDs 1 and 2 are ON and you heard the startup sound, but LED 3 is OFF, then the video card might be installed incorrectly or need replacement.LED 4 - Indicates that the computer and the LCD display panel are communicating. This LED will be ON when the computer is turned on and video signal is being generated. If the LED is ON and there is no image on the LCD display panel, the LCD display panel or inverter might be installed incorrectly or need replacement. And here’s the published process diags.pdf So where does that leave us?? I’m suspecting your GPU board is shorted out as the most probable iMac Intel 21.5" EMC 2389 GPU Card Replacement
