If the rest of the system is still connected, it's not some sort of backfeed from the standby 5V line is it? RP On 15/11/06, gacrowell@micron.com wrote: > Worked with an Intel server system that did the same thing but kept up > about 3V. Became a problem when the keyboards would lock up. Intel's > solution? Beat up the keyboard vendor to change their controller reset > threshold. Never mind that some customer is later going to change > keyboards and have problems. > > Gary Crowell > > > -----Original Message----- > > From: piclist-bounces@mit.edu > > [mailto:piclist-bounces@mit.edu] On Behalf Of Howard Winter > > Sent: Monday, November 13, 2006 9:12 AM > > To: PICLIST@MIT.EDU > > Subject: [EE] PC Power Supplies - stray voltage on +5V > > > > I tried building a device into a PC which was powered from > > the +5V line on one of the disk drive power connectors, and > > found that it was very > > unreliable in starting up - more often than not it didn't! > > > > So I put a meter on the connector and found that when the PSU > > has mains connected, but is turned off, there was 1.8V on the > > 5V line, so powering > > the PC down and up does not power the device I mentioned down > > properly. From cold it seems to work if you connect the > > power lead and then press > > the power-button within a couple of seconds - more than that > > and it locks up the device. > > > > I tried another PSU and that was showing 0.8V and had the > > same problem. I know there is a separate 5V Standby supply, > > but I would have thought > > that the main 5V should drop to zero when power is off, shouldn't it? > > > > Has anyone else encountered this? Am I likely to find a PSU > > that does behave "properly"? > > > > If not I'll have to use the +12V and put my own 5V regulator > > in-line, which will be annoying but will solve it (the +12V > > line does drop to zero). > > > > Cheers, > > > > > > Howard Winter > > St.Albans, England > > > > > > -- > > http://www.piclist.com PIC/SX FAQ & list archive > > View/change your membership options at > > http://mailman.mit.edu/mailman/listinfo/piclist > > > > -- > http://www.piclist.com PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist