metal shield

[sim085]

Hello, I always hear about how Commodore always wanted to reduce cost. I also see how many people remove the metal shield from their Amiga. So I wonder, why did Commodore put the shield in the Amiga? Wouldn't they have reduced costs if they removed the top one at least? Did all other Amiga competitors have the same thing?

[Matt_H]

It was probably a regulatory/FCC requirement. Some machines did ship without the top shield. I wonder if its inclusion was related to the regulatory environment of the country where the machine was to be sold.

As an anecdote, I have a few US 1200s and a US 500 and they all have the top shields. My UK 600 came without a shield.

[Tellurium]

Because, you see, cutting on the RF shielding, they would not have passed EMC (electro magnetic compliance). This would have cut costs, but also potential markets. And stupid as it may seem, Commodore really wanted to stay in the US market. Even if death came from that market, hilariously

[sim085]

But am I wrong, the A1000, A2000, A3000, etc don't have such shields...

Because, you see, cutting on the RF shielding, they would not have passed EMC (electro magnetic compliance). This would have cut costs, but also potential markets. And stupid as it may seem, Commodore really wanted to stay in the US market. Even if death came from that market, hilariously

[wiser3]

The shields provides two way protection.

First of all the shield helps prevent the device from producing any emissions, (radio, electrical, etc...) that interfere with the operation of other devices.

Secondly the shield helps protect the device from emissions that other devices are allowed to emit.

Exact laws and standards of how much and what types of emissions are allowed vary from country to country. Without the shields these standards wouldn't be met, the device wouldn't get certification and would be illegal to sell.

[Matt_H]

But am I wrong, the A1000, A2000, A3000, etc don't have such shields...

I can't explain the A1000, but the other big box machines' metal cases may have served the same function as the RF shield in the smaller Amigas.

[kreciu]

Secondly the shield helps protect the device from emissions that other devices are allowed to emit.

Considering what I did to my A1200 motherboards in last 20 years, IMO they could survive anything .

[Oldsmobile_Mike]

FCC shielding.  IMHO unless you're working in a hospital or somewhere else that could possibly be sensitive to this sort of thing, toss 'em.  They just trap heat and cut your fingers when you open the system up to work on it.  But don't tell Scuzz that, I seem to recall he had a whole thread a few months back about how those metal shields are the greatest thing next to sliced bread.  :lol:

[scuzzb494]

FCC shielding.  IMHO unless you're working in a hospital or somewhere else that could possibly be sensitive to this sort of thing, toss 'em.  They just trap heat and cut your fingers when you open the system up to work on it.  But don't tell Scuzz that, I seem to recall he had a whole thread a few months back about how those metal shields are the greatest thing next to sliced bread.  :lol:

You will like this then ....

http://www.scuzzscink.com/amiga/scuzzblog_september17/scuzzblogdseptember17_1602.htm

[QuikSanz]

They used to think RF could cause undesired operation and interference on yours or others devices. Notice how now you can have your phone on in an airplane for example.

[Motormouth]

EM interference can be significant in some cases.   The FCC was particularly crazy about this in the 80's with so many computers and gaming systems coming out.   It was unclear what effect they would have like television or radio inference etc.  you also have to remember we were still using 12v and 5v lines had the "potential" (in this case both meanings) to radiate. and since the computer has signals of 10s of kilohertz to megahertz frequencies which are in the the radio/and TV bands and other communication bands of the era.  In the A500 the filter choke and the floppy cable are particular noisy according to my field meter.  

In an unrelated topic
@Tellurium,  Just curious why Tellurium, do you like the smell of onions?  Eventhough it is used in many things, tellurium is not the element most people think of.....

[a1200]

With the exception of an A600 with an accelerator, I always build/restore my Amigas with the metal shield on. One because it "completes" the build and second, being a radio ham, most Amiga clock speeds sit on a HF band (7MHz, 14MHz, 50MHz accelerators etc) so does raise the noise floor so try to keep it as suppressed as possible.

[arttu80]

I can't explain the A1000, but the other big box machines' metal cases may have served the same function as the RF shield in the smaller Amigas.

Maybe not very relevant, but A1000 is of plastic case construction (remember team member autographs underside of top cover?), it does have RF shielding.

[Matt_H]

Maybe not very relevant, but A1000 is of plastic case construction (remember team member autographs underside of top cover?), it does have RF shielding.

But wasn't the A1000 the only plastic Amiga to ship without metal RF shielding? What RF sheilding are you referring to on the A1000?

I wonder if the regulation was introduced post-1985...?

[Motormouth]

But wasn't the A1000 the only plastic Amiga to ship without metal RF shielding? What RF sheilding are you referring to on the A1000?

I wonder if the regulation was introduced post-1985...?

At least in the US  The regulations were pre 85.  Even the early system like the Atari VCS and Atari 800s had to meet specifications.  Particularly in the VHF and UHF bands ie 30 Mhz to 3Ghz (if my memory is correct) and the public radio air wave bands.

This of course only applies to the US.  Other countries has their own regulations, sometimes very stringent, sometimes non-existent
This is why the Commodore 128D  has a US version and an everywhere else version.  
The US version has a big heavy metal case.