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800xl_1984

Shielding in 800XL

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How necessary is the metal shielding inside an 800XL?

 

* I installed the Ultimate 1MB, so the top shielding won't fit unless I find some tin snips.

 

* I bought this board with a video upgrade, and I get some kind of short to the power system when I install the bottom shielding.

 

Thanks,

J.

 

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I don't think having the shielding matters much any more, but I was able to get the shield back in (with some Dremel work) on my 800xl. I didn't put it back at all in the 1200xl.

post-61189-0-76609600-1535286286_thumb.jpg

Edited by jc13
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Typically the RF shielding inside a vintage game or computer system isn't needed at all these days. Remember, these systems were meant to sit in typical living rooms, bedrooms and home offices in an era when OTA television signals were how the vast majority of people got their TV. The FCC didn't want these new-fangled video games and computers from interfering with that. These days the situation is vastly different. Why some folks still get their TV via OTA antennas, they do so with digital signals that are much less affected by the kind of analog RF "interference" produced by home computers and consoles.

 

So unless you just want to reinstall the shielding for aesthetic reasons, there really isn't much reason to do so. I do like to use the bottom shielding in my 1200XL with an Ultimate 1MB board, simply because otherwise the entire system feels a little less substantial than I'd like. By contrast, my 800XL (also with a U1MB) doesn't have any of the old shielding in it at all.

 

Your mileage may vary ...

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Thanks to both of you. Didn't want to burn the house down or sterilize myself. :-o

Edited by 800xl_1984
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My 600XL has no shielding at all. I left only the bottom shielding in my U1MB 800XL because it didn't really get in the way at all and I liked the feel of the extra weight. Both operate just fine and don't show any interference. Only my original 800XL has all of its shielding intact but that only because I don't want to do any modifications to that machine at all.

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Shield can be useful if you're having grounding issues on unstable systems (motherboard has no ground plane layer), but if everything works without it, you can leave it off.

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I have bottom shielding on mine still, no top, no room, and I'd have to cut at least half away if I wanted it, so I don't see much point in half-shielded anyway. But as JFC said, I keep the bottom shielding for grounding purposes.

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Usually when you bung upgrades into the machine or run certain peripherals. I had a U1MB 130XE which only worked reliably with the original SIDE cartridge if I attached the bottom shield. There's no real need to go looking for issues. If something's not working, you'll notice soon enough. :)

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If you still use the RF output, the shield *may* may help keep the picture noise free. you'll have to evaluate the difference. If you use the monitor output, you probably won't notice any difference.

 

Small mods I have just cut a hole in the top shield, but my current 800XL project has too many mods I'll probably ditch the top shield entirely...

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I always keep as much shielding as possible, there are a number of reasons to do so. It keeps interference out, and keeps the Atari from propagating interference itself, it also keeps a decent ground mass for certain devices. It only ever helps, it never hurts. The idea that new television digital signals are impervious is not true. In marginal areas the signals can and do prevent a good picture to a greater extent, The signal still travels on good ole analog waves with digital information on those waves. Digital signals are no where near as robust as the old system which handled errors as a normal course of life, a little static, snow, or noise didn't make it un watchable or unintelligible. Digital tv pixelates and dies at signal levels well above the old way of doing things. spurious noise and pops gets you a hot mess onscreen in a heartbeat.

 

Live near a radio station tranmitter? TV transmitter? or Ham radio operator? No shielding at all causes problem for you and them. The harmonics of many signals are picked up from your computer and from their equipment. This is leading to some re-implementation of some of the old rules. There have been a number of threads explaining good reasons to keep the shielding with far reaching crazy conversation going down to the effects of back ground solar radiation or some such things and their effects on chips, proms, etc.

 

This kind of thing has led to stuff working fine at one persons location and having issues when it finds a new home some where else. You never know if someone will use the rf modulator on and old tv etc. either and the shielding has been known to make a difference for the better in those cases.

 

I think the dremel work you did is more than fine, the shielding isn't really diminished as the u1m is acting as a shield to a degree itself, ground / power plains are part of the lower noise design of todays PCB work when done by competent people

Edited by _The Doctor__
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If you use a CRT monitor. I do. It is better to put as much shielding back as possible. Plus the grounding is always good to have.

When I do testing on open boards, I do see distortion showing on the CRT screen.

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Thanks for the insights on the reasons to reinstall the shielding. Any thoughts on why the bottom shield might be shorting the power system and, more importantly, how I can avoid it? Can't screw the case closed with the bottom shield installed or the power won't come on.

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In that case, it sounds like some portion of the shield not insulated by the card is touching the board, or the insulation material is punctured.

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Bottom shield is still under my 600XL but more for ground plane and weight reasons then anything else.

 

My metal-backed keyboard does the rest.....LOL kidding....

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@level42.... the metal backed keyboard used to be touched by tabs, as were cart doors on xl's some had a green ground wire or spring screwed to them... so you are not far off :)

 

You can always run a ground wire to to metal keyboard, unless someone got sloppy with conductive paint or paste that is ;)

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there really isn't much reason to do so. I do like to use the bottom shielding in my 1200XL with an Ultimate 1MB board, simply because otherwise the entire system feels a little less substantial than I'd like. By contrast, my 800XL (also with a U1MB) doesn't have any of the old shielding in it at all.

 

Your mileage may vary ...

 

Well, if you've any amateur radio operates in the area it is just common courtesy to replace the shielding.

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Well, if you've any amateur radio operates in the area it is just common courtesy to replace the shielding.

 

None that I'm aware of, no large antennae poking above any of the local suburban landscape and no one has come knocking, so … no. :)

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