>On Apr 25, 2009, at 4:49 AM, Ernest L. Gunerius wrote: >> >> Hi Bill; >> >> Do not feel abashed, there are many mysteries in Switch Mode power >> supplies. They gave me many 100 hour work weeks, intense headaches, >> sleepless nights and good pay for 20 years. >> >> The advent of Wall Worts and Bench Bricks came about so that >> Equipment designers no longer had to fret and stew over International >> Regulations involving Safety Qualifications with attendant costs and >> Liabilities associated with the Switch Mode Power Supplies. >> >> The Green Wire(line grounding pin) is usually tied to >> Equipment(Chassis) ground. Circuit DC ground is tied usually at one >> spot to equipment ground. That takes care of Static potentials. >> >> Secondary(low voltage) Isolation is by the High Frequency >> Transformer. This is the expensive Componant to design since it must >> with hold a quite high DC voltage (at least during qualifying tests) >> with thick insulation while maintaining tight coupling. >> >> To each his own, >> >> ErnieG > > >So I'm guessing there's really no discharge method for a capacitor in >a psu? Maybe that's what the original poster also wants. > >I'm sure the others as well as me, appreciate your expertise. I have >an HP type psu that could use a fan (or 2 as I have learned with this >thread) replaced, but we chose to buy a whole ps-unit and replaced >that in his HP awhile ago ... mainly because of the uncertainty and >danger of electric shock. > >My main concern is whether something like this can be solved for a >professional amateur like myself (someone who successfully replaced a >QS 2002 Dual 1GHz mobo, PCI cards, AGP video cards, completely >disassembled/reassembled a Yikes! for cleaning, etc), and maybe >others listening as well, over a forum discussion like this ... sort >of borders on "Don't Try This at Home" kind of thing. I never >disassembled the psu. > >Maybe overkill on the warnings (borderline pun intended). > >Bill Connelly >artsite: http://mysite.verizon.net/moonstoneartstudio >myspace: http://www.myspace.com/moonstoneartstudio
Bill; Someone on this thread mentioned unplugging and letting the computer sit for at least 30 minutes or overnight would be better. The Capacitors should be discharged by then. I don't have a Power Supply out side of a Computer to look at. While similar, they are all different in any case. If you do not have experience with Electronic testing using Voltmeters to find dangerous terminals in Power Supplies I would suggest you not attempt any of these Fan replacements. If you are comfortable with the Instructions then you are on your own. The one Hack I looked at, where the Input and Output Air openings were cut to remove Grill work, seemed to me to make the Computer un-saleable since the Safety requirements were violated. Back in the day, 50 years ago, there was a test device known as The Finger which was an articulated replica the size and shape of a 10 year old's finger that was used, on new prototypes, to probe all openings to see if any dangerous live Voltage could be touched from the outside of the case. I would imagine today the finger should replicate a 4 year old finger. At age four I performed my first Electrical experiment which started the grey in my Mothers hair. I managed to blow a 30 Amp Screw in type fuse in the house service entrance along with copious smoke and a flash of light at my testing site. I did find the answer to my question though. As designed and as selected by the Computer Manufacture all components are Guaranteed to function. Some Computers are louder than others. If noise is troublesome that should be a before purchase decision. If the Fan has become inoperative some of the Electrolytic Capacitors could also be drying out and becoming leaky in which case a new Power Supply will be needed. HTH, ErnieG --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed Low End Mac's G3-5 List, 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] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/g3-5-list?hl=en Low End Mac RSS feed at feed://lowendmac.com/feed.xml -~----------~----~----~----~------~----~------~--~---
