Apple MD094LL/A Manual Do Utilizador

iMac (27-inch, Mid 2010) Symptom Charts — Startup and Power 

 2010-09-09

3.  Press power button while 

monitoring diagnostic LEDs. 

Verify if LED #2 turns ON and 

remains ON after pressing 

the power button. You may 

alternately check for a power 

request signal between pin 12 

and pin 1 of logic board.

Yes

Power supply functioning and 

logic board detects supply 

voltages. Go to 

 symptom flow.

No

Go to step 5.

4.  Disconnect AC cable. Remove 

glass and LCD panel, and 

carefully inspect the connectors 

between AC inlet and power 

supply, then DC connectors and 

cables between power supply 

and logic board, for damage or 

poor connections.

Yes

Reseat misconnected cable(s), 

or replace damaged one(s).

No

Replace DC power cable 

harness.. Go to step 8.

5.  Inspect power button and 

verify if it is properly connected 

to the logic board.

Yes

Go to step 6.

No

Reconnect power button.

6.  Disconnect power button from 

logic board. Inspect cable and 

connector for damage. Using a 

multimeter (set as ohmmeter), 

verify continuity between the 

two pins of the power button 

when it is pressed.

Yes

Power button is functioning 

correctly. Reconnect power 

button to logic board and 

go to step 7.

No

Power button faulty. Replace 

rear housing (which includes 

power button).

7.  Press power button and Verify 

if system turns ON. You may 

alternately check for presence 

of a 12V DC signal between 

pin 11 and pin 1 of logic board 

when power button is pressed.

Yes

Power supply functioning. If 

system still won’t boot, go 

to 

 symptom 

flow.

No

Replace DC power cable 

harness. Go to step 8.

8.  Press power button and verify if 

system turns ON.

Yes

Issue solved with replaced DC 

power cable harness.

No

Replace power supply. 

Go to step 9.

9.  Press power button and verify if 

system turns ON.

Yes

Issue solved with replaced 

power supply.

No

Reinstall power supply and 

replace logic board.

Note: If No Power symptom persists after all steps have been followed use minimum 
configuration troubleshooting to proceed. Try disconnecting hard drive(s), optical drive, AirPort, 
Bluetooth, and SD card modules to determine if one of them is preventing the power supply 
from functioning.