To shield, or not to shield?

[WxAxNxDxExRxExR]

Coming from the C64 world, it feels natural to detach and safely store the original cartoonish cardboard 'shielding' never to attach it again.

 

Atari models, on the other hand, have some substantial ones, so what is your advice regarding XL/XE models -- keep or remove?

[TGB1718]

No need to remove unless your fitting some sort of upgrade, removing seems to have no detrimental effect.

[Beeblebrox]

For the 400 and 800, which have substantial heavy metal shielding and because they are integral to the structure,those are always kept.

 

Personally for the 600xl, 800xl, 65xe, 130xe and 800xe, I remove the shielding completely. This is mainly because often I have upgrades going inside, and sometimes putting the shielding back is tricky, not possible.

 

Tbh these days the original main point of the shielding is no longer needed, since modern displays and interferance is no longer a real issue, compared to displays used decades ago.

 

I have however, read about shielding improving the overall grounding.

 

 

 

 

[+mytek]

If for some reason you still wish to use the RF output (TV channel 3 or 4), then the shielding is required. The reason being that you will likely see some pretty terrible interference patterns on the screen without it.

 

For those that have no intention of ever using the RF output, and instead will be using a monitor (Composite or S-Video), or one of the analog/digital variants (VBXE, Sophia, or LumaCode), and you don't care about that HAM radio operator across the street - there is no need to keep the shield.

[Bobo Cujo]

Does removing the RF modulator completely remove the need for the shield (even for the HAM Radio operator across the street case)?

[Peri Noid]

Removing an RF modulator on an XE machine is equivalent to removal of Composite signal. Just keep it in mind. 

[Rybags]

I've only removed it to make room for VBXE and Ultimate 1 Meg on my 800XL.

The shielding is beneficial both ways, also can reduce incoming interference to your computer.

 

In the analog TV days my desktop PC was in a plastic case - this lack of shielding was sufficient that the computer would interfere with just about everything in the room.

[_The Doctor__]

The shielding apart from the rf/em aspect, is structural, stiffening the Atari preventing PCB flex damage, and the bent keyboard failures that we see from time to time on AA. The shield also provides electrical mass. This has been covered in many posts outlining it's form and function, it is always best to keep as much shielding as possible on the Atari line of computers. It works for me today does not mean it works for me tomorrow or 5/10/20/30 years from now (or then)

[CommodoreDecker]

11 hours ago, _The Doctor__ said:

The shielding apart from the rf/em aspect, is structural, stiffening the Atari preventing PCB flex damage, and the bent keyboard failures that we see from time to time on AA. The shield also provides electrical mass. This has been covered in many posts outlining it's form and function, it is always best to keep as much shielding as possible on the Atari line of computers. It works for me today does not mean it works for me tomorrow or 5/10/20/30 years from now (or then)

 

 

Yep. The wonderfulness of DC current grounding.   Systems might seem to work stable now, but down the road there might be instability. I recently upgraded an 800XL for s-video, and an 1200XL (5v bypass, ROM v11, svideo fix, etc...  except extra RAM since who needs more than 64kb? ) and was tempted to remove the shield forever.  It's still in a cupboard. It's going back in. 😇

 

Well, 256kb or 1mb can be very, very useful - I remember the days of RAM drives on the 130XE, but for regular use/gaming, 64 works for almost everything ever made for it back in the day.

Edited January 21 by CommodoreDecker

[ACML]

I keep my shields on.  Not to hijack the thread, but 64K for me is really enough.  If I want to play 64K or 128K XE carts, I use the UNO cart which works great on stock 64K machines.  Even larger CAR or ROM images can use the Ultimate cart on a 64K machine.  Not planning to use word processors or spreadsheets bigger than 64K limits anymore.  Also, some 256K DRAMs discharge slowly and you have to leave the power off for 3-5 seconds to ensure a cold start.

 

Edited January 21 by ACML

[+CharlieChaplin]

Marvel: We want SHIELD

Startrek: Shields on

Atari: I am a fearless XL/XE Star Raider and fly with shields off.

 

 

[+mytek]

23 hours ago, CommodoreDecker said:

On 1/20/2024 at 9:12 PM, _The Doctor__ said:

The shielding apart from the rf/em aspect, is structural, stiffening the Atari preventing PCB flex damage, and the bent keyboard failures that we see from time to time on AA. The shield also provides electrical mass. This has been covered in many posts outlining it's form and function, it is always best to keep as much shielding as possible on the Atari line of computers. It works for me today does not mean it works for me tomorrow or 5/10/20/30 years from now (or then)

 

 

Yep. The wonderfulness of DC current grounding.   Systems might seem to work stable now, but down the road there might be instability. I recently upgraded an 800XL for s-video, and an 1200XL (5v bypass, ROM v11, svideo fix, etc...  except extra RAM since who needs more than 64kb? ) and was tempted to remove the shield forever.  It's still in a cupboard. It's going back in. 😇

I think we need to verify some of this information before assuming it is absolute. All too often I see stuff preached or held as gospel based upon incorrect or hearsay evidence.

 

I have two 65XE systems one with an intact shield, and one without. I need to reassemble the keyboard on the one without (currently retro-brighting key caps) and put it back together. Then I'll do a twist test in multiple directions to see if one is noticeably more structurally stiffer than the other. However of all the benefits attributed to leaving in the shield, this one and the minimization of visual interference when using the RF output are likely true. But I need to prove the structural aspect to myself before citing this as essential to leaving in the metal shield. The visual interference of the RF output without the shield I've already seen, and appears to be quite true.

 

Quote

The shield also provides electrical mass.

This is a rather open ended statement that really doesn't mean a whole lot in itself. So are we to presume that because it is tied to the system ground that this 'extra mass of metal' is somehow making the system more reliable? If that's true, than the flooded ground planes on the board are insufficient to do the proper job. And if that's the case, then Atari did a very poor PCB design, since you should never rely upon shielding to make up for insufficient current transmission in the ground planes of a PCB.

 

Quote

It works for me today does not mean it works for me tomorrow or 5/10/20/30 years from now (or then)

I really doubt that this applies to a shield or no shield situation. Can you present some actual evidence of this really happening? Like what is it that will cease to function or become unreliable as a factor of time going by if the shield is left out?

[+mytek]

Ok so I just completed a series of tests with a 65XE, and here are my results...

1. STRUCTURAL TEST: No discernible difference with or without shield (removed bottom and top shield). Also had zero influence on keyboard strength since the shield makes zero contact with the underside of the keyboard (it rests on the inside front area of the case and two plastics posts that stick up in the rear).
2. RF OUTPUT INTERFERENCE: Unfortunately my camera ran out of juice to take a picture, but I definitely could see some herringbone patterns traveling across the screen without the shielding in place. Mileage may vary depending upon the TV being used.
3. NON-RF VIDEO and AUDIO INTERFERENCE: No additional noise was seen or heard.
4. ELECTRICAL MASS: The PCB Ground Plane has an extremely low resistance over distance, being on the order of .004 ohms as measured from one side of the PCB over to opposite side with no shield in place (based on these results I saw no need to test with the shield).

I used my Lab Quality HP3466A MultiMeter in it's mili-ohm mode to obtain readings...

 

10 ohm Reference with 1% Tolerance Metal Film Resistor

Zero Point Test (shows how much resistance the test leads add)

Across the Board Test

 

In conclusion here's what leaving in the shield adds...

When RF Output (TV Channel 3 or 4) is desired, it is definitely required to minimize screen noise. And if you don't want to cause interference with someone close by listening to either weak AM or FM radio transmissions over an aerial, the shield should be retained (however now days this concern is probably negligible, and should be dealt with on a case to case basis).

 

Making a Case for Leaving out the Shield...

At least where an Atari XE is concerned, it does not add any significant and/or observable structural strength to the overall case, or to the keyboard. It does not cause any interference to the Composite or S-Video output, and it does not add any additional background noise to the audio. The added metal mass of the shield does not appear to add to the integrity of the ground plane on the PCB (not really sure how it could based upon what my mili-ohm tests showed).

 

As for structural aspects where an XL is concerned, my feeling is that the XE would be most prone to being weak as compared to the XL systems due in large part to the thinner plastic and fewer screws holding the case halves together. Also in the XL, the keyboard is attached with screws to the underside of the case top and doesn't appear to rest on the shield, and it also has a metal backing plate. So I doubt there would be any structural side effects of leaving the shield out of an XL as well.

 

The Atari design employees considerable RF/ESD filtering networks that I've never seen an externally generated RF noise source cause any hiccups with the computer's operation.

 

Bottom line, leaving out the shield makes it infinitely easier to add upgrades to the Atari, and/or diagnose problems.

 

It would be nice to put a lot of the folklore about whether to shield or not finally to rest. Of course as per usual there will be those that disagree with my assessment - so be it, at least I tried to apply a scientific method

[Beeblebrox]

Thanks for testing all this @mytek

I'd imagine very few A8 users use rf as a video output so as you say if you are using composite or other means there doesn't appear to be a problem running an XE minus the shielding.

 

Personally from a practical standpoint having the shields in place is a pain when I have some upgrades place/and or not possible to keep because of them. For example my 600xl has u1mb, Sophia2, stereo, etc, so retaining the one piece tight sheilding wouldn't really be possible/practical without some serious mods to said sheilding. Even then you run the risk of shorting something out.

 

Interesting to see structural benefits of shielding don't appear to greatly make a difference to the XE range. The XE cases are generally quite rigid and the pcbs seem to benefit from this rigidity already when all assembled.

 

In terms of the keyboard on XE's it kinda makes sense that are quite rigid on their own, mainly as a result of the keyboard's metal base plate and the rest of it made of fairly rigid plastic too. Plus the notches either side of the XE casing support the keyboard well as it sits inside the casing. 

 

I have quite a bit of experience with dealing with 800XL and 600XL keyboard variants and I actually have come across a good few of the metal backed membrane ones which have bowed in the middle, even with sheilding in place. Doesn't happen with non membrane ones but I can imagine they must bow and as such microcracks could occur in the keyboard pcbs over time, causing issues. I think the shielding here would help to limit how much they might bow and flex because they all have rectangular rubber stick down to the shielding to help stop this it seems. The XEs also sometimes come with these. Then again, typing a lot on a8s isn't as likely as BITD, so not really an issue. 

 

On balance I think I'll stick to removing the sheilding on mine as I've been doing, possibly with the exception of the 1200xl given they are so damn rare, and of course the 400 and 800, since the solid aluminium Faraday sheilding is a core structural element.... and kinda looks like the Deep Thought super computer from Hitch Hikers Guide to the Galaxy Heh Heh...

 

 

 

[+David_P]

On 1/20/2024 at 4:36 PM, mytek said:

For those that have no intention of ever using the RF output, and instead will be using a monitor (Composite or S-Video), or one of the analog/digital variants (VBXE, Sophia, or LumaCode), and you don't care about that HAM radio operator across the street - there is no need to keep the shield.

That HAM operator - she's two doors to the north, actually...

[+Stephen]

2 hours ago, mytek said:

STRUCTURAL TEST: No discernible difference with or without shield

Not surprising.  It's ultra thin sheet metal gently held together with squeeze tabs.  You don't need a degree in Mechanical Engineering or mechanical sciences for this one.

[+mytek]

3 hours ago, Beeblebrox said:

I have quite a bit of experience with dealing with 800XL and 600XL keyboard variants and I actually have come across a good few of the metal backed membrane ones which have bowed in the middle, even with sheilding in place.

No surprise since the shield doesn't touch the bottom of the keyboard, so how could it possibly support it.

 

EDIT: Well at least in my XLs there's a space between the shielding and the keyboard. I guess if it bows enough it'll touch.

[Beeblebrox]

4 hours ago, mytek said:

No surprise since the shield doesn't touch the bottom of the keyboard, so how could it possibly support it.

 

EDIT: Well at least in my XLs there's a space between the shielding and the keyboard. I guess if it bows enough it'll touch.

The space is taken up by black rubber rectangular spacers glued to the sheilding. Often found on 800xl and 600xl and occasionally on XE sheilding. Probably made of condensed dark matter Heh Heh! 😁

 

 

[+mytek]

10 hours ago, Beeblebrox said:

The space is taken up by black rubber rectangular spacers glued to the sheilding. Often found on 800xl and 600xl and occasionally on XE sheilding. Probably made of condensed dark matter Heh Heh! 😁

 

Interesting I've never seen that. Mine all came without the rubber spacers. Must have been a down the road fix that got implemented.

[Beeblebrox]

3 minutes ago, mytek said:

Interesting I've never seen that. Mine all came without the rubber spacers. Must have been a down the road fix that got implemented.

It might be a PAL machine thing. All 800xl and 600xl pal machines that have come through my hands have one or two of them. I've got a massive pile of these rubber blocks. To a far lesser extent you see them occasionally on pal XE models. 

[Havok69]

Being a HAM myself, I of course shield. 

 

It's also always a good idea to reduce your exposure to EMF (also why I'll never buy an EV!)

 

https://pubmed.ncbi.nlm.nih.gov/27012122/

[+remowilliams]

My habitual deshielding is finally officially validated!  😄

[+mytek]

49 minutes ago, Havok69 said:

Being a HAM myself, I of course shield. 

 

It's also always a good idea to reduce your exposure to EMF (also why I'll never buy an EV!)

 

https://pubmed.ncbi.nlm.nih.gov/27012122/

Interesting article, but it is unrealistic to think humans can escape this reality. Everyday millions of people place calls from cell phones - to towers - which relay signals to other towers - and finally to the intended target cell phone. Then there's public WiFi, satellite internet, AM and FM radio station transmissions, HAM radio broadcasts, Television broadcasts, and the list goes on and on. Compared to all of these sources of radiation, the Atari is but a very small blip on the radar.

 

There is a small town west of where I live that was going to have public WiFi in its downtown. Several citizens in that town went to great lengths to block it and succeeded in doing so. All the while claiming that they would have been exposed to deadly radiation otherwise. Funny thing was, it was reported that several of the opposition owned cell phones - go figure

 

BTW, before you worry about possible harm from your Atari or EV, think how close your cell phone is to your brain each time you make or take a call.

[Brentarian]

[Overange]

If you are really concerned about EM Radiation pouring out of your modded Atari, one option would be to paint the inside of the case with a copper conductive paint.

 

https://www.amazon.co.uk/Electrically-Conductive-Spray-Paint-Copper/dp/B07DC9KFTP

 

This would help reduce the amount of EM being emitted.

 

And to confirm this theory, just put it inside your anechoic chamber and measure away.

 

Oh and do not forget your foil hat.