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 Post subject: [rant] EMI/EMC: Did I Miss Something?
PostPosted: Thu Dec 06, 2012 4:16 pm 
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Joined: Mon Nov 05, 2007 5:31 am
Posts: 19
This has been bugging me so I thought I'd solicit other views...

My previous build, about 4 years ago, was an Antec Solo. Not perfect but good enough.

Now I want to build a home/media server and decided on the Fractal Design Define Mini. It arrived quickly but the motherboard etc. would be a few more days. So I took the opportunity to explore. Everything that is not painted black is painted white. Cool look. Then I decided to check the grounding. Oh, what grounding? The only metal visible is inside the motherboard mounting holes. Even the PSU mounting is painted (powder coat?) and has a foam gasket. The side panels and the pressure fingers in the frame are all painted too. None of the panels are electrically connected to any other. Even the rivets are painted.

I was shocked. What does this do for electrical safety, EMI/EMC or ESD?

When I built the Solo, the word on the street was EMC (electro-magnetic compatibility) and how EU regulation was going to inflate equipment costs with extra approvals, wave-guide fan vents etc. The Solo has panels that are painted only on the outside. Everything else is plated steel, probably zinc with a chromate wash. Good conductor. Bright spring steel tabs around the frame rails rest on paint free areas of the side panels. Nice folded seams. All fan vents have a punched grille. All in all a good “Faraday cage” design with all panels providing a protective ground, RF reference and an ESD path.

Looking at the Fractal case I can't see why they bother making the panels out of metal.

Then I started looking for an alternative and discovered that this in now the norm, even for Antec.

What am I missing? Were Faraday and Maxwell wrong? Is that portion of the RF spectrum unused (Ha!)? Are we not supposed to put two computers near each other? Does anyone care? Anyone got the number of a good therapist?

So what am I missing? The money. Paint or powder-coat the panels before assembly and you can skip the expensive plating and masking steps in manufacture. That's why they cost less now. The manufacturers have “approval” and put the various marks on their packaging secure in the knowledge that no-one is going to check.

My opinion is that a Quiet PC should also be RF quiet.

Feel free to comment, agree, disagree, educate or “rip me a new one”.

--Dave_G.


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 Post subject: Re: [rant] EMI/EMC: Did I Miss Something?
PostPosted: Fri Dec 07, 2012 2:47 am 
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Joined: Mon Mar 17, 2008 1:49 pm
Posts: 1189
Location: UK
Dave_G wrote:
The manufacturers have “approval” and put the various marks on their packaging secure in the knowledge that no-one is going to check.

Approval is more complex than that and CE marks don't just get given away. You have to demonstrate that it performs to some specification. If you want to challenge them to prove it, they should be able to give you all of the documentation. Fraudulently claiming approval that you don't have would be a very serious business and no one would be stupid enough to do that.

It's fine, you're overreacting.

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 Post subject: Re: [rant] EMI/EMC: Did I Miss Something?
PostPosted: Fri Dec 07, 2012 6:39 am 
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Joined: Sat Nov 23, 2002 6:33 am
Posts: 8636
Location: Sunny SoCal
Aren't we already having a discussion on this exact same topic in this other thread:

viewtopic.php?f=23&t=65467

Both threads were even started by Dave_G.

??

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Music Server: Intel DH77EB + i3-3220, 2xSamsung 2TB F4, Pico PSU, Fractal Define Mini, 2xScythe Fans @250 rpm.


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 Post subject: Re: [rant] EMI/EMC: Did I Miss Something?
PostPosted: Sat Dec 08, 2012 1:48 am 
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Joined: Mon Nov 05, 2007 5:31 am
Posts: 19
The other post was my initial reaction to having no grounding on external metal panels. Here I'm just trying to understand why my reaction was wrong.

I can assume from replies, or the lack thereof, that this is not an issue.

I guess advances in clock speeds have seen improvement in signal handling on the motherboard and low voltage differential signalling, PATA->SATA, HDMI etc. mean the box now needs to do less shielding.

Thanks of listening,
--Dave_G.


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