MP 1,1-5,1 [fixed] Mac Pro 5,1 PSU high pitch noise

[arw]

Hey, this is my first thread and I just wanted to share my observations in case anyone else experiences the same.

I recently acquired/upgraded to a Mac Pro 5,1 2010 Dual socket.
I immediately noticed a very high pitch noise which was extremely annoying and audible even across the room.
It seemed to come from the PSU so I opened it up and localized the source with a paper tube.
The culprit were 3 interference suppression capacitors (MKP-X2 0,47µF 275V).
Although they are based on metallic polypropylene, I found a blog entry of Corsair where they explain that these capacitors can indeed emit high frequency noise. (in german only: PSU noise - Corsair explains)
So I invested 5 € and swapped them out. Easier said than done as Delta uses higher temperature solder and I had to use a much higher rated soldering iron.
I replaced the fans beforehand to reduce as many other sound sources as possible (aftermarket-fans-with-automatic-smc-control).
I recorded the soundstage before and after the swap (with my old iPhone) and attached the spectrogram of the relevant frequency range.
The audible difference is as gigantic as the image suggests.
If this seems like an unsafe and foolish action, please tell me.
Edit: Before any attempt, please read the comments, safety first!

 

[KeesMacPro]

Very interesting find!

As long as the capacitor is the same type, same value and equal or higher voltage, there's absolutely nothing unsafe or foolish about it , as long as there's nothing loose and with open contacts
One tiny note though: the new capacitors have a different distance between the pins, so soldering them in the pcb is complicated/not possible.
At a major supplier like e.g. Mouser, RS Components etc one can search for a quality Cap with the same pin distance...

 

[Macschrauber]

And of course there must be a big warning.

Dont do this if you are not experienced with psu repairs. The big capacitors can seriously bite you.

I use a classic light bulb to discharge them. You will get visible response and get remembered how much load they can hold.

Nice find, indeed. I never had such a noisy psu. Another way to find such vibrating components is to hold a plastic (!) stick at the component and on the ear.

 

[KeesMacPro]

The big capacitors can seriously bite you.

I use a classic light bulb to discharge them. You will get visible response and get remembered how much load they can hold.

That's exactly how I do that when working with power amps (audio) , the Caps can hold the voltage (up to 100 Volts) for very long time...

 

[arw]

One tiny note though: the new capacitors have a different distance between the pins, so soldering them in the pcb is complicated/not possible.
At a major supplier like e.g. Mouser, RS Components etc one can search for a quality Cap with the same pin distance...

That is a very helpful hint I was not aware of!
I added extension cables to make it work.

And of course there must be a big warning.

Dont do this if you are not experienced with psu repairs. The big capacitors can seriously bite you.

I use a classic light bulb to discharge them. You will get visible response and get remembered how much load they can hold.

Nice find, indeed. I never had such a noisy psu. Another way to find such vibrating components is to hold a plastic (!) stick at the component and on the ear.

You are definitely right. I let it sit for 2 days and used gloves but the light bulb method is without a doubt a better solution.
I will keep the plastic stick in mind, great idea.

 

[Macschrauber]

Even after 2 days (regarding if there are unload resistors connected or not) the big Cs can hold voltage.

Its not only the voltage what harms the human, if you make shorts while soldering and handling the pcb you might kill other components and traces with the 300 volts from the Cs.

 

[arw]

You definitely got a point there. Although I paid attention to not short anything, in retrospect, I was lucky and learned something from you for the next time.
MacRumors forum is just great!