On Aug 30, 11:26 am, [email protected] wrote: > If the PSU fan proves to be the noisy one, replace the PSU. > > The PSUs are considered "non-serviceable" as there are lethal voltages > inside, even after the ac power has been removed. > > The potential across some components is over 325 volts.
sounds like advice from someone selling PSUs, or else . . . . this discussion has appeared on the lem lists before, in regard to servicing emacs and other all-in-one boxes that contain a CRT. there is no danger if you follow simple guidelines, and minimal danger of mild discomfort if you ignore them. voltage does not kill. amperage kills. there is not enough stored energy in a QS power supply to stop the heart of a mouse. if you want to be anal and drain the capacitors in the PSU before opening it up and replacing the fan, simply quit all applications and then pull the power plug while the computer is still running. this effectively depletes all the charge stored in the PSU capacitors and causes no more harm to the computer than if a power outage had occured. less, because there is no voltage spike that might be associated with a power outage. the PSU fan can then be safely replace by even the most bumbling idiot. but it's not really necessary in the first place. just be careful not to touch any of the exposed contact points while the PSU is open. but even if you did, the only thing you MIGHT experience is a brief tingling sensation. no worse than putting a 9v battery on your tongue. in the past, this debate has been conclusively settled by listers who reported being zapped by the capacitors for a CRT, which may be charged to potentials as high as 25,000 volts with nothing more to show for it than a good story. again, voltage does not kill or cause injury. if you stand beneath a typical 1350 volt power line, the potential between your head and your feet is much greater than 325 volts, and you experience no sensation whatsoever. amperage kills. and there is not enough stored energy in the PSU to generate sufficient amperage at 325 volts to cause more than a tingling zap, and whatever amount of current does flow, it will drain the capacitors in a fraction of a second. it takes far more than that to kill or even cause injury. for crying out loud, a few people have survived attempted execution in the electric chair, and thousands have survived direct lightning strikes. stop and think before you post. common sense should tell you that your irrational fears are unadulterated weapons grade baloneyium. you can believe who you choose, but i am a university professor, trained in chemistry, physics, mathematics, instrument repair, and my father was a commercial electrician. -- You received this message because you are a member of G-Group, a group for those using G3, G4, and G5 desktop Macs - with a particular focus on Power Macs. The list FAQ is at http://lowendmac.com/lists/g-list.shtml and our netiquette guide is at http://www.lowendmac.com/lists/netiquette.shtml To post to this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/g3-5-list
