Have an iMac G5 1.8 ghz operating on 10.4.11 that keeps switching itself off - particularly after increased fan noise. After putting it into sleep mode it more often than not won't switch on again (even though can hear fan noise) unless powered off and re-started. Any ideas? Likely costly repair?
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imac g5 1.8 cutting out
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you very likely if you lay down the iMac screen down on something soft (dont want the display scratched ) turn the 3 screws on the bottom (they dont turn out complete ) to the stop and then just lift on the the stand up , then will see either some leaking capacitors or bulging ones , or if you take out the powersupply (careful when opening it not to get electrocuted ) inside it some leaking or bulging capacitors
its a well well known problem since the very first iMac G5 hit the market , up to 2008 apple even offered a repair scheme which ran out in 2008 , so yours is 2 years to late to get it repaired for free ,
but even if you had been earlier you might only have found out about that repair scheme if you specifically had asked for it at a apple store, as apple always avoids to get these repair schemes made public
the replacement capacitors are cheap as chips , just need new caps soldered in which cost here in the uk at any shop which had specialised in that repair around the £170 mark , if you are lucky to know someone who can do it it will be cheaper , or if you can solder yourself its really cheap to repair
and as a small note to anybody who is tempted to buy a iMac G5 , as they are cheap to get now ,
1. YES if the owner can proof it had the logicboard exchanged by Apple
2. YES if the owner can proof the iMac g5 had ALL the capacitors replaced by a authorised Apple repair technician
3. YES if you have good soldering skills
only if you can answer one of the 3 points with a yes then its worth buying iMac G5 as they are still great Mac's only let down by the bad capacitors
so if it had a new logicboard, then the culprits are very likely to be found in the powersupply . as that will cause the now waking up from sleep
and eventually not power up at all
the little pram battery under the airport card could be dead too
its at the iMac g5 where you have to look for hardware reasons before you start to look for software problems , on other iMac's the problems are often only software related
and eventually not power up at all
the little pram battery under the airport card could be dead too
its at the iMac g5 where you have to look for hardware reasons before you start to look for software problems , on other iMac's the problems are often only software related
sure you will get some more life out of it , its still fast enough for most things even youtube will run at least at 480p , thats enough really for a computer , you could even hook up a monitor and extend your desktop (apple only disabled screen spanning in open firmware to boost sales of the PowerMac ), but the little tool "screen spanning doctor" solved the problem by enabling screen spanning in open firmware again and you can extend the desktop over 2 screens , which comes handy
and another tip once its working again fine
use the " reduced " setting under options in energy saver under system preferences if you dont need all the power of the g5 ,its reducing the 1.8 ghz to 900mhz
it not only safes energy , it also is reducing heat , which means slower running fans ,near total silence and its easy to change back to automatic or highest if needed , so for pur websurfing (no youtube)or emailing or office work you wont notice a difference other then a quiet running, less heat producing iMac G5
and another tip once its working again fine
use the " reduced " setting under options in energy saver under system preferences if you dont need all the power of the g5 ,its reducing the 1.8 ghz to 900mhz
it not only safes energy , it also is reducing heat , which means slower running fans ,near total silence and its easy to change back to automatic or highest if needed , so for pur websurfing (no youtube)or emailing or office work you wont notice a difference other then a quiet running, less heat producing iMac G5
that was my intention 
i mean i dont want anybody be put off to buy a iMac G5 , as they are really good computers and fast for a computer from 2004 , and not neccesary the componants are totally bad , its the design thats causing the problem .
Apple had to find a compromise between a totally silent all in one as its sitting direct in front of the ears ,in a very slim case , if you for example look at the heatsink of the early powermac g5 desktops they have huge heatsinks and two fans to cool the same g5 processor , but that was not possible to manage in a all in one computer , imagine the size of it with such a huge heatsink , that would have created a huge hump on the iMac's back
so a smaller heatsink and higher temps , doesn't harm the G5's processor , the harddrive gets just enough cooling too , so do the other components inside , the trouble had been these bad capacitors , a capacitor has heat limit , if its a good capacitor it would be no problem at all to withstand even higher temperatures then the ones in the iMac g5 , but these bad capacitors do in very simple words corrode inside and then have a much lower heat limit , the result is they bulge or start leaking , problem all of them at different rates , so depending on room temperatures and all sorts of factors like usage , some start leaking in the first couple month , and others after years
i mean i dont want anybody be put off to buy a iMac G5 , as they are really good computers and fast for a computer from 2004 , and not neccesary the componants are totally bad , its the design thats causing the problem .
Apple had to find a compromise between a totally silent all in one as its sitting direct in front of the ears ,in a very slim case , if you for example look at the heatsink of the early powermac g5 desktops they have huge heatsinks and two fans to cool the same g5 processor , but that was not possible to manage in a all in one computer , imagine the size of it with such a huge heatsink , that would have created a huge hump on the iMac's back
so a smaller heatsink and higher temps , doesn't harm the G5's processor , the harddrive gets just enough cooling too , so do the other components inside , the trouble had been these bad capacitors , a capacitor has heat limit , if its a good capacitor it would be no problem at all to withstand even higher temperatures then the ones in the iMac g5 , but these bad capacitors do in very simple words corrode inside and then have a much lower heat limit , the result is they bulge or start leaking , problem all of them at different rates , so depending on room temperatures and all sorts of factors like usage , some start leaking in the first couple month , and others after years