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Drilling holes in a 400 Faraday cage?


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I finally got my dream 400 (functional, relatively clean, stock) and have been hitting it with the upgrades. The UAV is very pretty and the TransKey-II sure makes typing easier when the nostalgia of the membrane keyboard wears off.

 

But that Faraday cage is a beast. I'm sure it did its job blocking RF signals back in the day, but it's also really effective at blocking any cables I want to pass outside the plastic. Has anyone tried to drill holes in a 400's Faraday cage? I'm thinking of using a 1/2" (~13mm) HSS drill bit. I'm hoping I won't have to invest in a cobalt steel bit, but that cage looks like it means business.

 

-Joe

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Aluminum Joe, your bit should be fine, though I would suggest using a smaller bit as a pilot and working up to your 1/2"

 

 

This does bring up a question, not sure if this thread is the right spot.. but is the shielding on these computers to prevent RF getting out? or RF getting in and messing with it?

 

Makes me wonder in the modern world if there is not more Ghz, and mhz and BT and wifi signals out and about that there would be more worry about RF getting in than out??

 

I know people have just removed MB and mounted them in a PC case.. if you do a UAV, and just remove the RF signal generator, should that not be fine.. and you could even ditch the Shields?

 

James

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The original intent by the FCC was to prevent RF from escaping the computer and becoming RFI at someone's TV antenna. Remember, these old rules were made before many people had cable TV, and still used antennas.

 

As far as leaking IN, I don't think there would be much of a problem considering we're using 5V TTL logic. The voltage induced by the PCB traces would likely be too low to trigger a logic high.

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It would be difficult to eliminate the aluminum cage from the 400/800, it acts as the support for parts of the upper case, the 800 card bay cover attaches to it, etc.

 

Rather than drilling a hole through the aluminum, why not put a notch in an edge so a cable can exit between the cage and the circuit board. This method doesn't require routing the cable through a hole before making connections, just have to position the cable properly during assembly.

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Back when I added the RetroKidz SVideo adapter board to my 400, I added extra cooling holes to the cage. Its pretty simple.

 

The original thread is here: http://atariage.com/forums/topic/163005-a400-composite-mod/?hl=%2Batari+%2B400+%2Bsvideo&do=findComment&comment=2026954

 

There is a picture of the cage after I added the holes here: http://atariage.com/forums/gallery/image/4471-img-2851jpg/

 

I just used a 3/8 drill bit on a power drill. It cut through in just a few seconds. But take it slow to get a good clean finish.

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I would pick up some of these...

image_11761.jpg

Harbor Freight Item#91616 ($13.99 for the set)

 

These come in handy for all sorts of projects, and work especially good on aluminum.

 

I also like BillC's idea of making a notch, this would be best started with a hole that is then filed open on one side.

 

- Michael

Edited by mytekcontrols
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Rather than drilling a hole through the aluminum, why not put a notch in an edge so a cable can exit between the cage and the circuit board. This method doesn't require routing the cable through a hole before making connections, just have to position the cable properly during assembly.

Oo! I like this idea. Would I still use a drill, only change the location of the hole to an edge, or can you recommend a better notching tool?

Edited by Smokeless Joe
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  • 4 weeks later...

I finally got around to notching the cage on my 400. A hacksaw would have been the cheap and easy way, but I'd been wanting a Dremel for over 20 years, so I decided to treat myself and bought a Dremel 4000 kit. The EZ456 metal cutting wheel cut well at about 15,000 RPMs and was useful for detail work at 5,000 RPMs. I forgot to take a before picture, but the notch (on the right) can be compared to the other trapezoidal part (on the left):

 

post-36974-0-87524400-1463937845_thumb.jpg

 

It's not as pretty as I wanted it, but it'll be hidden once the case is back on. I'll probably want to soften the edges before reassembling so it doesn't saw through the cables any time they're moved. But it's very functional! It lets out the UAV S-video cable and the TK-II PS/2 cable, which is all I really wanted:

 

post-36974-0-40357800-1463938562_thumb.jpg

 

I was kinda planning on using the Dremel to make holes in the plastic case to mount the above plugs, but someone suggested using the original RF cable hole and just have the cables hang out, so I'll probably do that.

 

Anyway, that was fun!

Edited by Smokeless Joe
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