The iMac is a range of Macintosh desktop computers (all-in-one) by Apple Inc. It is one of the best and important part of Apple's consumer desktop computers since 1998-08 (shipped; intro 1998-05). In its first model, the iMac G3 had a CRT monitor, mainly enclosed by a coloured, translucent plastic case, which was refreshed early on with a sleeker design notable for its slot-loaded optical drive.
The second version the iMac G4 design, the base contain all the main components and an LCD monitor on a pivot arm attached to it. The third and fourth major models, the iMac G5 and the Intel iMac respectively, contain major components (logic board) behind the display, creating a slim design that tilts only up and down on a metal base. The fifth major model shared is thinner and uses anodized aluminum and a glass panel in the front.
The newest iMac however, uses a different display unit, without the SuperDrive. It is ultimately thinner than older models, with an edge thickness of 5.9mm. Also includes a dual microphone setup, and SSD or HDD storage, or an Apple Fusion Drive, a hybrid of solid state and hard disk drives.
The latest model was announced on October 23, 2012, with the 21.5" version released on November 30 and the 27" version released in December; these were refreshed on September 24, 2013, with new Haswell processors, faster graphics, faster and larger SSD options and 802.11ac WiFi cards.
Some of the problems with iMac desktop computers include;
It is almost impossible to update older iMac Mac OS x 10.4.11 online. For example if your iMac is running Mac OS x 10.4.11. You won’t be able to download from app store because the Mac Os is too old. A PPC (G4 or G5) iMac can upgrade only as far as Leopard 10.5.8. If yours is an Intel based iMac you can go directly to Snow leopard 10.6.8:
It is almost impossible to update online. For example if your iMac is running Mac OS x 10.4.11. You won’t be able to download from app store because the Mac Os is too old. A PPC (G4 or G5) iMac can upgrade only as far as Leopard 10.5.8. If yours is an Intel based iMac you can go directly to Snow leopard 10.6.8:
Late 2013 27" iMac, yellow screen issues - Some users have reported problems with the new iMacs having the yellow screen problems. Some people using Apple iMacs (late 2009) have been experiencing issues such as cracked glass, flickering displays, yellow tinged screens, noisy screens, CD/DVD drives scratching discs, drive failures, etc.
iMac flickering and dark screen problems - If you have a Late 2009 27" iMac and are having problems with those annoying problems of flickering and parts of your screen are becoming darker (On the left side primary) you may want to consider Apple iMac repair at AppleLap UK to fix it if you run out of warranty.
27" iMac won't boot past white screen - Have any issues with your iMac late 2010 27" model.
Apple iMac 27″ Dark Side Screen Failure - More recently though the quality of the OSX updates have been less than perfect and its starting to feel a bit like Microsoft all over again with regular OS updates that need a computer re-boot.
iMac condensation inside screen glass - 24" aluminum iMac and after about an hour of using it, a 1" x 3" strip of condensation gradually appeared in the lower right portion of the screen behind the glass. iMac screen gets frozen and becomes completely unresponsive – Most users wouldn’t know what to do here. iMac running Mac OS 10.8.4, have this weird problem from time to time.
iMac motherboard problem: The machine does not boot, it does power up when pressing the power button, hard disk spins and optical drive makes the usual sounds it should. However, fans do not spin; they both make one small rapid movement but do not spin normal. Also if you connect a USB device, like backlight keyboard, the backlight will blink quickly , every time. The machine will stay in this dead state. Heat sink gets warm.