Most likely like you say it's from the power supply, most likely it has to do with one of the capacitors on the power supply reaching it's natural end of life, at this point they may start to give incorrect voltages and also start humming, worst case scenario they will swell and crack, sometimes with an audible popping noise. Of course it could also be from a capacitor on the main board but the power supply is my guess.
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Most likely like you say it's from the power supply. It's probably one of the capacitors on the power supply reaching it's natural end of life, at this point they may start to give incorrect voltages and also start emitting a humming sound like you describe, worst case scenario they will swell and crack, sometimes with an audible popping noise. Of course it could also be from a capacitor on the main board but the power supply is my guess.
Most likely like you say it's from the power supply, most likely it has to do with one of the capacitors on the power supply reaching it's natural end of life, at this point they may start to give incorrect voltages and also start humming, worst case scenario they will swell and crack, sometimes with an audible popping noise. Of course it could also be from a capacitor on the main board but the power supply is my guess.