Model A1418 / Late 2012 / 2.7 & 2.9 GHz Core i5 or 3.1 GHz Core i7 Processor

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What is chin strap and it's purpose?

What is chin strap and its purpose?

When do I need to remove chin strap?

of iMac 21.5 late 2012, and early 2013

iMac 27 late 2012

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Chin strap for the 21.5" 2012 iMac.

This casing strip aligns the bottom edge of the display to the rear housing unit. The lower VHB (Very High Bond (VHB) Strips attach to it. This holds the display in place.

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Its seems to both force the air circulation out into the CPU and also to stop EMI interference.

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However, it's yet not altogether clear to me what the purpose of the chin strap is.

To understand its purpose, it may be helpful to understand how the iMac air circulation works:

The iMacs with a chin strap, including the iMac Pro, have a single big fan that sucks air from the vents at the bottom edge of the rear housing and blow it out through the grille on the back of the rear housing. Thare aren't any other vents nor grilles to take air in or out.

So, its first purpuse seems be to stop air coming in from the vents on the bottom edge of the rear housing from going into the space between the display and the logic board, so forcing it to go under its ideal circulation through the CPU and then to the fan, then blown out through the grille on the rear housing. (Notice that the fan is located very close to the CPU and the fan mouth is attached to a plastic housing that faces right into the CPU).

On the other hand, the chin strap comes with the same black curled tape band (not sure how to call this, the service guide for iMacs doesn't even mention it) all around the rear housing, which seems to be intended to stop any EMI (electro-magnetic interference) from coming into the unit.

Notice that in the picture the chin strap has been removed, it's just where the down arrow points.

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The chin strap is beneath the bottom edge of the display, so the display doesn't rest on it. It seems intended to hold the EMI (electro magnetic interference) black strips that surround the inside of the iMac.

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