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Diagnosis LED #1 keeps blinking after I had replaced the Power Supply (PSU) No chime, no fan activity, no “Electric buzz” on surface, like total dead iMac. I wonder how do I check the Ground of the AC inlet EMI filter, before I buy a new motherboard. I checked with multimeter the AC inlet EMI filter cables that suppose to connect to the MB and I see voltage, that mean the positive/live line pass through the AC inlet EMI filter but I don’t know how to check the ground line… Because from the AC inlet come out a Green cable that is attached to the external surface, and I can’t feel anymore the electric buzz when I touch when it was working normal, always feel like a little buzz. Could the ground line malfunction cause the LED 1 blinking and do not start at all? Could be the EMI filter AC inlet be the reason? I would be happy to find any suggestion before I decide to do something
@samuelmgm12 to check your EMI filter use an ohm meter. Measure from one prong of where you connect the power cord (line)to one of the output lines past the EMI filter (load). You should get around 0.4 ohm. Same with the other prongue. Remember that there will have to be continuity. Measure from any of those points to the case of the filter. Your meter will either show a 1 or OL because there should be no continuity (shortcircuit if it does). The green cable is actually the ground wire. You can check the ground the same way. One lead to the prong (line) and the other on green wire should give you a OL on your meter (no continuity). You can check both prongs to ground. Yes, a failed filter will not allow your AC power to pass. In that case your iMac should not display any LED. LED#1 lighting up means that power is available.
The power outlet is a straight through wired with the pig-legs wires to the power supply. Each line has a Ferris choke to clamp down the EMI emissions. Tyco - Power line filter (first order filter) I haven’t needed to replace the part other than one time when someone bent the ground pin snapping it. I would use a DVM and with the system turned off and fully assembled and with one lead touching the case and the other touching a good known ground point do you see any AC voltage present?
