Is the metal shielding required in all-in-one Amiga models?

Question

All-in-one Amiga computers (500, 600, 1200) have metal shielding surrounding the mainboard. It is in two parts, one below the mainboard and one on top. The mainboard is physically linked to the lower part by the hex bolts that are either side of most of the rear I/O ports and the screws that attach the mainboard to the lower plastic outer case. Then the upper part of the shielding attaches to the lower part by bending small metal tabs to hold it in place (a bit like the metal tabs on the back of most types of picture frame).

What are the consequences of not fitting and using the metal shielding? Either no shielding at all, or fitting just the lower shielding and removing the upper part.

I expect that this means that it would probably fail some EMI emissions tests in some countries, meaning that the manufacturer would not get permission to sell the computer. Let's disregard this aspect since the manufacturer is no longer making and selling these computers. What are the practical aspects that I, as a user, would see?

• Would the computer still operate normally with either or both parts of the shielding removed, or is the shielding necessary for operation? (e.g. by connecting electrical ground to different parts that require it)
• Would the computer still be reliable, or would EMI interference cause noticeable effects such as crashes?
• Would other nearby electrical devices be affected in any noticeable way by the Amiga's EMI emissions?

Answer 1

Amigas work fine without their metal shields, and even the big-box machines' innards can be taken out of their case and run open on the desk. I never noticed any instability on my old A500 with the shield removed, although I might have done were I a radio amateur running a powerful transmitter nearby.

As to the Amiga's emissions, FCC rules forbade Commodore from selling into the American market without RF shielding. The UK had no such rules, and if you look at British machines of that era, they omitted shielding and the machines stomped all over the medium-wave and HF bands. An Amiga without shielding can be expected to do much the same.

These days, the HF band is a toxic wasteland anyway due to Powerline kit and other cheap and nasty electronics, so you can't make it any worse by removing your Amiga's shield.

Answer 2

Anecdotally, I would advise against removing it. My Amiga 500 started crashing when I did large movements in front of it (standing up from a sitting position or walking by) after having the shield removed. Putting it back in stopped the behaviour.

Answer 3

Quote from Stephen Craimer who worked at Los Gatos before and after the Amiga Launch when he saw this question.

"I also worked with on the FCC issues, both for the Amiga and after. unless the law has changed, the interference you cause by removing a shield opens you up to a Law Suite in a residential context. The AMIGA was a noisy beast, it used high power TTL bus drivers on relatively long wires."

The UK boxes had the shield painted on the plastic.

So I do not recommend it, unless you build a Faraday shield, wrap it in grounded Aluminum Foil, or probably when operating the Amiga in a commercial context (office building) all at your own risk.