Power supply issue - making buzzing/zapping sound while operating

Question

DJstylus Author

Level 1

15 points

Power supply issue - making buzzing/zapping sound while operating

I recently bough a S/H Mid 2010 Mac Pro (single processor model).

The person I bought it from told me that it had had an "issue" in the past to which he (himself)

replaced the power supply but it didnt fix it.

It then had the main logic board replaced at an Apple store & that fixed the "issue" (he never told me

specifically what the issue was).

The machine does 2 things:

1 - when you plug the power cable into the back of the machine (power supply), there is a quick little

zap sound & the computer automatically begins booting up.

It will shut down/bootup/sleep/wake as normal once it has started for the 1st time after being plugged in.

2 - there is a (ongoing) buzzing/zapping sound coming from the power supply area once the machine is operating.

It doesnt seem to affect the operation of the machine, & Ive had it on for 8hrs or more doing file transfers from my older Mac Pro, but none the less the sound is still there & Im pretty sure it shouldnt be...

What is the best way to determine what could be causing the automatic booting up when you plug the power cable it, & what the buzzing noise is coming from the power supply itself?

I can try & record a video of it & up load it here if that's helpful.

Im reluctant to get rid of my 3,1 Mac Pro until I know 100% the 5,1 isnt going to explode or anything like that...

thanks in advance

Mac Pro

Posted on Dec 22, 2018 1:33 AM

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Answer 1

Dec 22, 2018 10:00 AM in response to lllaass

There is an "always-on" power supply in the Mac. The arcing when inserting the cord is normal.

I agree with llaass that it may be starting up based on "startup automatically after power fail" setting.

--------

I have car-repair tool that looks like stethoscope, except that it ends in a 6-in rod, not a diaphragm. It has been generally useful for many things over the years.

You put the earpieces in your ears, then take the rod and apply it to various surfaces inside the running Mac, and listen. The noise will change on each surface, and when you hear the one directly making the noise, it will be loud and clear.

All the different fans and drives (and as mentioned the door itself) may be contributing or resonating.

The power supply typically controls it own fans. If they are dusty, they could be noisier.

The approved method for dust removal is to move your Mac to a place where dust is a don't care, and use compressed air to launch the dust bunnies up and out of your Mac.

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Answer 2

lllaass

Level 10

210,513 points

Dec 22, 2018 3:25 AM in response to DJstylus

For noise, maybe these will help:

https://forums.macrumors.com/threads/power-supply-buzzing.1088918/

https://www.dpreview.com/forums/thread/2778142

https://forums.macrumors.com/threads/mid-2010-mac-pro-humming-noise.2026817/

https://forums.macrumors.com/threads/mac-pro-8-core-power-supply-making-noise-like-refrigerator-radiator.825636/

For startup in System Preference>Energy Saver>Power is the box that say Startup automatically after power failure checked?

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