Model A1200 with 2.16 or 2.33 GHz Core 2 Duo processor

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iMac - turning on but screen is black and no sound

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?

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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?

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No UPS or other power devices. Directly to the power plug. No lightening. I think this is age of iMac. (((


Surge suppressor & UPS can protect your system i.e. Power supply. While you do need to replace the power supply consider getting a good surge suppressor at least for your system and system's peripheral devices. Yes, age can also be the cause but more often I see power surges as the issue.


Dan, thank you for your attention. But all 4 diagnostic LED's lit up! Why? I am ready to buy new power supply but not sure about this decision.


OK that does change things. Lets start the diagnostic process again here. Review this Apple TN and tell us how far you get: Intel-based Mac: Startup sequence and error codes, symbols


Dan, thanks. Great article but nothing useful for me. All that I hear and see after pressing power button:

1. Power LED on and slow down off - absolutly normal.

2. DVD-ROM sound.

3. Coolers start working on maximum speed.

4. I hear special electronoise like turning on LCD display, but nothing on the screen.

5. That's all - no boot chime, no HDD reading sound - nothing, only noise of coolers.


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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.

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