Black screen,loud fans, LED 3 off

Question

iMac G5 20" Model A1076

1.8 또는 2 GHz G5 프로세서

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Johson @capkz

평판: 11

1

게시됨: 2020년 3월 30일

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Black screen,loud fans, LED 3 off

My problem is when the power cable on, the LED’s #1 & 2 are on, hit the power button, I get the Bong sound, but LED #3 &4 are off, the fans is normal, but after half past minute, the fans begin ramping up with a loud noise, screen still black.

Is the problem is logic board or the LCD display? If the LCD display is ok, I want to change it just like a display

I removed the HDD, so I don't know how to run diagnostic services, can you tell me? I will be very appreciative.

Here is what I did, I connect the keyboard and try to hit the cmd+alt+r+p, buttons and power up the system. I also tried hitting the button under the CD player, even changed the battery on the logic board, nothing worked.

I’m desperate now, maybe the logic board has a problem, the price is high now in eBay for a replacement, so if I can know the LCD display is good, can I transfer it to a screen to let my Mac Mini use it?

So,here is my problem and questions if someone can give me some help I would appreciate it.

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Dan @danj 평판: 489.3k Self employed contract worker 35 338 973 · Answer 1 · 2020-03-30T05:39:55-07:00

The onboard diagnostic LED’s are a bit different in the older G series systems, here’s the breakdown:

LED 1: Indicates that trickle voltage from the AC power inlet to the power supply has been detected. This LED will be ON when the computer is turned off and your power supply is working correctly.
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 main logic board has established communication with the LCD display.
LED 4: Indicates a processor over-temperature condition. The system will shut down when this LED turns on.

So, if you’ve disconnected the display panel LED #3 & 4 will not be lit. LED #4 would be on if the system was overheating.

The fan will also race as SMC has lost access to the display thermal sensors so the system goes into Safe Mode, pushing the systems cooling into high gear.

Did you run diagnostics services off of the gray CD that came with your system.

You will need to put the HDD back into the system as you need both the thermal sensor mounted on the bracket to be re-connected you also need the OS files on the drive to run the system.

To run diagnostics you’ll need the original gray CD’s that came with your system. One of them has the diagnostics on it. But from what you are now describing you have deeper issues here'. Its likely your Inverter and/or the screens CCFL backlights are not working.

This is going to need deeper diagnostics and parts to fix this system. There is a point when fixing is not cheaper either cost or time. I’m sure this is the case here, sorry.

I would strongly recommend you look at spending the money on a better system, new or used.

In any case the display can’t be really used on your Mac Mini with out adding a lot of expense. Again, a newer LED back lit 14” display would be cheaper.

iMac G5 20" Model A1076

Black screen,loud fans, LED 3 off

Update (03/30/2020)

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