On 9 Dec 98 at 21:28, Kenneth J. Kovler wrote: > On Wed, 9 Dec 1998, David Gillett wrote: > > > > PC power supplies are supposed to shut down if there is a high > > impedance across the 5v supply. This could indicate an electrical > > fault within this drive. I can't imagine any other way it could > > affect the system without the ribbon cable attached. > > I think you mean "low impedance" here. this implies if a short were to be > placed across the power supply +5v the supply would shut down, thus > protecting from burning up tracks on the pc card and internals to the > supply. Well, the temperature alarms that we installed last year *claim* that they throw a high impedance across the 5v supply to shut down the power supply. In order to do this reliably, they insist on being on a separate power lead -- if they used a short, the presence of other devices on the lead wouldn't impair their effectiveness, so I don't think it's a documentation error. Certainly a short *should* cause the power supply to shut down, and that may be what's happening in his drive.... David G The PCBUILD web site always needs good submissions. If you would like to contribute to the website, send any hardware tech tips or hardware reviews to: [log in to unmask]