why does my old pc keep reverting back to 2003 on start up

[Wheeler777]

oh so you say thier not rechargeable, i dont wish to argue the point, but you might tell these people :-

http://www.microbattery.com/laptop-n...-batteries.htm

W

[TechWreck]

Originally Posted by TheCoder

Not specifically although I believe some of the later Gigabyte and Dell branded boards have the very simple modification. Its basically just an extra capacitor and a couple of extra diodes. Probably no more than 2-3 pence in component cost.

The circuit is exceptionally simple, using a diode OR arrangement to select between battery power or capacitor power. Once the capacitor loses charge so its voltage is lower than the battery (battery is usually a CR2032 3V lithium cell type) then the battery takes over

1/ When PC power is on capacitor charges from 5V rail via a diode, so it gets to around 4.4V (0.6V diode drop). A small resistor can be used to limit initial current through the diode if necessary (not needed for a small value capacitor - dependant on RAM current draw and time you require). The diode also serves to prevent the capacitor from attempting to power the 5v rail when the PC power is switched off.

2/ Capacitor and battery are connected together, each through a diode, to the RAM standby voltage pin. The battery will be able to supply around 2.4V though the doide (0.6v diode drop from 3V) so as long as the common point (where capacitor and battery diodes are connected together - the RAM standby voltage pin) stays above 2.4V then the battery diode will be reverse biased - no battery current flows. This will occur whilst the capacitor stays above 3V. With a RAM device that only takes a few nanoWatts of power than can be a significant amount of time !

So, 2 extra diodes and a capacitor and you get yourself hours to days of no power taken from the battery. The value of the capacitor and the standby current requirements of the RAM determine how long you get before the battery is required to take over.

Coder that is electronic porn! lol
love it think I got a twinge !