iMac G5 (20" with iSight) just gave and bang and smoke came out of it...

This has been reported before - google for "exploding iMac".

G5's were replaced with Intels more than 6 years ago. I think the cost of repairing would be more than the cost of an equivalent replacement.

I think this computer would not be cost effective to repair:

* it sounds like there was significant hardware damage inside the iMac. These computers (like laptops) have lots of hardware packed closely together. The smoke you saw was from something that burned or overheated, which means other components were likely damaged as well, in close proximity.

* You would need to have someone check and test all major components for damage. This will not be inexpensive because you need to pay for the technician labor.

* Once the issue is diagnosed, you'll need to buy parts that have to be replaced. SInce IMac G5 major components are no longer manufactured, you'll need to find them somewhere. Logic boards, power supplies and the like cost from $50 to $500, depending on what they are and the source, but it is most likely that they will be used, probably taken from older, broken computers like yours in fact. This does not bode well for future longevity. If the screen itself and high voltage element has blown, that can be quite expensive.

* There is also the cost to have someone replace the parts, reassemble, and test.

* Adding this all up, it is likely to be a significant fraction of the cost of a new Mac, which starts at ~ $1000. Plus the reliability of such a repaired unit is questionable, while with a new Mac you get a machine that may be 5 times faster, will have more storage and memory, and will have a warranty, and is likely to last 5 or 6 years or more.

You can fairly easily open up the iMac G5 yourself with just a screwdriver and inspect the components.

I'm familiar with this because I have an iMac G5 from 2005 and its logic board just failed last week. It's not worth repairing.

First of all, do not plug this iMac in again until and unless Apple tells you it is okay. It is potentially hazardous to you.

Second, contact Apple using www.apple.com/support/contact if you are in a country that supports it or call the appropriate phone number on this page. Alternatively carry the iMac in to an Apple retail store or service provider.

As this may be a safety issue, I can pretty much guarantee they will want to hear about it.

Best of luck.

Same happened to me yesterday and I went to my nearest Apple store to have it checked (IMAC bought in February 2009). They were concerned but useless and I would have expected a replacement. Apple customer support is not helpful and after having been a loyal customer for a lot of years I may now move to PC if they do not take safety issue seriously !

Hi all an update of my situation I am incredibly satisfied with Apple customer service. I received a phone call yesterday from the apple store yesterday and was advised that they were so concerned by the safety issue that they wanted me to come with my iMac (out of warranty) to be replaced by a new one and they even offered to give back my hard disc so none of my data would be lost !!! I am really impressed by this fantastic customer service ! I ll keep you updated when I get the new computer but I already bought some credit card for my daughter to download more apps from Apple store and I will stay a loyal customer ! well done APPLE !!! And thank you.