An intermittent like this would tell me it is a bad/loose connection someplace. Could be corrosion on a connector or switch. Could be a bad solder. Unfortunately, it is a hunt and peck process. I would open it up to have access to the MB, then connect an adapter, hold the power button and start tapping around the MB lightly with the handle of a screwdriver. If there is no reaction, repeat tapping a little harder. Hopefully, it will come on and you can narrow it down to a specific location or part. Good luck.
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An intermittent like this would tell me it is a bad/loose connection someplace. Could be corrosion on a connector or switch. Could be a bad solder. Unfortunately, it is a hunt and peck process. I would open it up to have access to the MB, then connect an adapter, hold the power button and start tapping around the MB (and/or a power board if there is one) lightly with the handle of a screwdriver. If there is no reaction, repeat tapping a little harder. Hopefully, it will come on and you can narrow it down to a specific location or part. Good luck.
An intermittent like this would tell me it is a bad/loose connection someplace. Could be corrosion on a connector or switch. Could be a bad solder. Unfortunately, it is a hunt and peck process. I would open it up to have access to the MB, then connect an adapter, hold the power button and start tapping around the MB lightly with the handle of a screwdriver. If there is no reaction, repeat tapping a little harder. Hopefully, it will come on and you can narrow it down to a specific location or part. Good luck.