The electronics website iFixit on Friday downgraded the new 21.5-in. iMac's repair score to 3 out of a possible 10, calling servicing the computer "an exercise in disappointment."

The website urged do-it-yourselfers to look for a leftover 2011 model instead. "Hackers, tinkerers, and repairers be forewarned: Get last year's model if you'd like to alter your machine in any way," said Miroslav Djuric, iFixit's chief information architect, in an email announcing the site's teardown of the newest iMac.

Apple started selling the redesigned 21.5-in. iMac on Friday at its retail and online stores. The larger, more expensive 27-in. iMac is to ship later this month.

After disassembling the iMac, iFixit assigned the all-in-one desktop a repair score of just 3 out of 10; The 2011 version of the same-sized iMac sported a more DIY-friendly score of 7 out of 10.

The iMac's new score is in the same low range as Apple's 15- and 13-in. Retina-equipped MacBook Pro laptops, which earned a 1 and 2, respectively, this summer and fall. In June, iFixit called the 15-in. MacBook Pro "the least-repairable laptop we've taken apart."

Explaining the iMac's low score, iFixit cited the copious amounts of "incredibly strong" adhesive that bonds the LCD and front glass panel to the frame. Earlier iMacs fixed the display in place with magnets rather than the hard-to-dislodge glue, which is even harder to replace.

Just as damning was an Apple design decision that makes it practically impossible for users to upgrade the iMac's RAM. The 21.5-in. iMac comes standard with 8GB of memory -- and can be upgraded to 16GB -- but because the RAM is buried beneath the logic board, owners must "take apart most of the iMac just to gain access," iFixit said.

Older 21.5-in. iMacs had four external RAM slots that were easily accessed by users.

Apple mentions the impracticality of memory upgrade only in a side note hidden on the iMac's options page. There, Apple said: "Every 21.5-inch iMac comes with 8GB of memory built into the computer. If you think you may need 16GB of memory in the future, it is important to upgrade at the time of purchase, because memory cannot be upgraded later in this model."

The not-yet-available 27-in. iMac will continue to sport four external memory slots. Customers can boost the RAM at the time of ordering to 16GB (for an extra $200) or 32GB ($600), but those prices are exorbitant compared to third-party RAM that users install themselves. An additional 8GB of memory -- which would raise the iMac's total to 16GB -- costs just $40 at Crucial.com, for example.

iFixit spotted several other changes to the iMac, including a larger, single fan rather than several smaller fans; dual microphones, likely a noise cancellation move for FaceTime video calls; and a vibration-dampening housing around the laptop-sized 2.5-in. hard disk drive.

The teardown also exposed the location where Apple places a "Fusion Drive," the option that combines 128GB of flash storage with a standard platter-based hard drive.

The new iMacs are priced between $1,299 and $1,999 -- $100 more than their precursors -- and can be purchased or pre-ordered at Apple's online and retail stores.

iFixit reduced the repair score of Apple's iMac from 7 to 3 (out of 10), citing screen-to-chassis glue and the impracticality of upgrading RAM or swapping drives. (Image: iFixit.)

Gregg Keizer covers Microsoft, security issues, Apple, Web browsers and general technology breaking news for Computerworld. Follow Gregg on Twitter at @gkeizer, on Google+ or subscribe to Gregg's RSS feed . His email address is gkeizer@computerworld.com.

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