Ir para o conteúdo principal

Model A1311 / Mid 2011 / 2.5 & 2.7 GHz Core i5 or 2.8 GHz Core i7 Processor

425 Perguntas Visualizar todos

No power on iMac

hello, I changed the power supply why led #1 did not light up, I want to clarify that... the led lit for 0.5 sec and went off... I bought a second-hand power supply here in ifixit but, the same thing happened, this source that I bought has a tick sound as if it is shorted, I wonder if it could be the motherboard that is damaging the power supply? Or did they give me a damaged power supply?

Responder a esta pergunta Também tenho esse problema

Esta pergunta é pertinente?

Pontuação 0
Adicionar um comentário

1 Resposta

Pergunta Mais Útil

@aliaudio1

LED Functions

LED #1

Indicates that the trickle voltage from power supply has been detected by main logic board.

This LED will turn ON when you connect the iMac to a working AC power source. The LED will remain ON as long as the computer is ON or asleep.

When computer has been correctly shut down, the LED#1 behavior may differ:

• - If a startup event is scheduled in System Preferences > Energy Saver, LED#1 will stay ON after a correct shutdown,

• - If no startup event is scheduled in System Preferences > Energy Saver, LED#1 will turn OFF and will stay OFF as long as power cord is connected and AC power source is present.

Disconnecting the power cord and plugging it back will turn back this LED ON , even if computer is still off.

After disconnecting and reconnecting the AC power source, this LED could remain OFF if the AC power source is missing or disconnected, if the logic board is disconnected from the power supply or from the AC outlet, or if the power supply board is faulty.

LED #2

Indicates that computer is turned on. This LED will be ON as long as computer is turned on (but is not asleep) and power supply and voltage regulators are working correctly.

LED #3

Indicates that computer and video card are communicating. This LED will be ON when computer is communicating properly with video card. If LEDs 1 and 2 are ON and you heard the startup sound, but LED 3 is OFF, then the backup battery (on front of logic board) may need to be reseated, or the video card might be installed incorrectly or needs replacement.

LED #4

Indicates that computer and LCD panel are communicating. This LED will be ON when computer is turned on and video signal is being generated. If LED #4 is ON and there is no image on display, then LCD panel, LED backlight board, or cables between LCD and logic board or backlight board might be installed incorrectly, or need replacement.

LED Startup Sequence

LED #1 = Power available.

If first LED is not lit:

• Disconnect the power cord from computer, then reconnect it to reset the LED status.

• Verify AC power source.

• Verify known-good power cord is connected.

• Verify cable connection between AC inlet and power supply.

• Verify cable connection between power supply and logic board.

• Verify power supply.

LED #1 + #2 = Power available, and computer is powered on.

If second LED is not lit when power button is pressed:

• Verify power button cable connection to logic board.

• Verify power button functionality.

• Verify cable connection between power supply and logic board.

• Verify power supply.

• Verify logic board.

LED #1 + #2 + #3 = Power available, computer is powered on, and video card found.

If third LED is not lit after power on:

• Verify that video card is seated properly.

• Verify if startup sound is present and fans are running when powered ON (reset SMC and PRAM, reseat or check backup battery if necessary for proper startup):

If POST startup sound is not heard, go to No Startup symptom flow,

If POST startup sound is heard, go to No Video symptom flow.

LED #1 + #2 + #3 + #4 = Power available, computer is powered on, video card found, and internal LCD found.

If fourth LED is not lit after power on:

• Verify internal DisplayPort cable connections between LCD panel and logic board.

• Inspect all LCD cables for damage.

• Verify external video functionality, and according to result check the following items:

If external display works then verify/replace the LED backlight board.

If external display works then verify/replace the LCD panel.

If external display does not work verify/replace the logic board.

So if you have checked everything on this list and knowing that the logic board "senses" the power from the power board, it is possible that the logic board does not detect the power.

Here is where the DC sensors should be located on your board

Block Image

Esta resposta foi útil?

Pontuação 1
Adicionar um comentário

Adicionar a sua resposta

davo1977 será eternamente grato(a).
Exibir estatísticas:

Últimas 24 horas: 0

Últimos 7 dias: 0

Últimos 30 dias: 1

Duração total: 26