Chosen Solution
Hi there! My iMac worked without any problems for 7 years. A few days ago has sharply turn off the screen. On pressing the power button there was no response. Disassembled case, when plugging in burned one diagnostic LED. Reinstall the memory. Started on and lit up all 4 LED’s, fans worked well, audible diagnostics of DVD but black screen and no sounds from speakers. No sounds of HDD reading. The question is what to change the inverter, motherboard or video card?
As you state the HD is not starting up either (no startup bong) I suspect your power supply is gone. Remember you have multiple low voltage taps so some ares of the system may be working while others not. But the real question here is why your power supply went. Do you have a surge suppressor or UPS? Did you get hit by lightening?
This was about the end of the period of the bad capacitor issues but I’d look at the capacitors on the power supply and elsewhere, and see if any are swollen or leaking.
