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buzzing noise coming from fan when holding power button

hi guys

I have a clients 2012 12” MacBook Pro here, I have never seen an issue like this before.

What happens is if you press the power button once the processor fan shakes for a second then nothing, if i hold my finger down on the power button the fan will spin but nothing happens no lights no display or anything but also I can hear a faint buzz noise coming from fan area?

Things I have done already (removed hard drive, removed ram) still the same

Here’s a short vid of the issue: https://vimeo.com/533800594

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Given the systems age I would start with the basics, is the MagSafe charger LED lit and is it Amber or Green? If green move on to below, if not let the system charge or put in a known good battery (charged)

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The noise I here is likely a bad power inverter on the logic board. Fully remove the logic board give it a dusting and inspect for staining or damaged components. Focus on the IC’s and Caps.

Using a DVM measure the rail voltages are all of the present and at the correct values?

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Try this: disconnect the battery and mag-safe. Press and hold the power button for ten seconds. Reconnect the battery then the mag-safe. See if you get a spontaneous reboot.

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shane beard crwdns2934231:0crwdne2934231:0
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