>On Apr 24, 2009, at 11:33 PM, Ernest L. Gunerius wrote: > >> >>> On Apr 24, 2009, at 10:03 PM, Meghrouni Vince wrote: >>> >>>> >>>> Does time unplugged diminish the voltage? >>>> >>>> What should I look for to avoid? I'm sure this may seem >>>> obvious, but >>>> it is not to me. >>> >>> I would suggest consulting an expert electrician ... and one that is >>> familiar with computer power supplies. The computer repair centers >>> sometimes will share info ... even the ones repairing those Windoze >>> machines ... I think most power supply's function the same ... >>> although there are different styles: >>> http://www.atxpowersupplies.com/ >>> >>> Have you ever started plugging the power cord back into the back of >>> the computer, with the other end in an active power strip or wall >>> socket, and a NASTY spark jumps out to meet you? I believe that is >>> the capacitor(s) discharging. I do not know if this is a way to do >>> the deed or not ... I repeat, I do not know. >>> >>> Just more food for thought. >>> >>> Bill Connelly >>> artsite: http://mysite.verizon.net/moonstoneartstudio >>> myspace: http://www.myspace.com/moonstoneartstudio >> >> If you get a spark when plugging in a power supply that has been >> unplugged for at least 30 minutes it is most likely the charging >> current recharging the Power Supply Input capacitors. The only >> Impedance to input current to the discharged capacitors is the Input >> Filter(if present), The Rectifiers and the series resistance(very >> small) of the Input Capacitors. >> >> Thus the turned off and discharged Power Supply looks like a short >> circuit to the line voltage and the initial Inrush current can be >> quite large and also decays to a small value rapidly as the Voltage >> on the Input Capacitors rises. As the Power supply begins to switch >> and produce the output voltages(3.3 volt, 5 volt,12 Volt) then an >> extra pulse of current is drawn to charge all the capacitors on those >> voltages in the Power Supply and the rest of the Computer. >> >> This all happens quite fast, typically about 2 tenths of a second. >> >> The Power Supply cannot discharge back through the Power Line. The DC >> Voltage is isolated from the Line by the Rectifiers. >> >> HTH, >> >> ErnieG > > >OIC. I thought it was discharging through Grounding. Possibly a fatal >mistake ... > >See ... better to ask a Pro! > >Bill Connelly >artsite: http://mysite.verizon.net/moonstoneartstudio >myspace: http://www.myspace.com/moonstoneartstudio
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 --~--~---------~--~----~------------~-------~--~----~ 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 -~----------~----~----~----~------~----~------~--~---
