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Released June 2012 / Core i7 processor with Turbo Boost / Up to 1 GB GDDR5 Video RAM

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No external display output - even after replacing logic board...

I'm stumped on this one. I had a machine which intermittently failed to send output to an external monitor. I tried different adaptors and monitors on it. Eventually it was just out entirely and wouldn't display a signal.

So I replaced the logic board. To my amazement, the problem persisted. I tried SMC and PRAM resets but there was no change. I ran an ASD and it didn't show any issues over multiple test loops.

When I connect an external display, the internal display blinks out and back, as it normally would when detecting an external monitor and sending a signal to it. But it never gets a signal. System Preferences - Displays doesn't show that a display is connected.

Oh wise iFixians, do you have any idea what this could be?

Answered! View the answer I have this problem too

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Has the macbook by any chance seen any liquid damage in the past ? Since you replaced the entire board, I can think of just two possibilities..a faulty logic board purchased, but the odds would be against this chance or a short somewhere in your machine's other components. I would try disconnecting the lcd connector from the logic board and boot without it, just connected to the external since you got one available.

If that works properly the problem would be isolated to your macbook monitor..check if the connector to the board is fine with at least a lens and good light to make sure of its condition. It could also be some lcd component is damaged creating problems all along the line.

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