Replacement of Proprietary Dell Supply with Generic

First of all, we were astounded by just how simple this was.

Dell power supplies use an extra connection to identify the supply and a Dell laptop will reject a supply that it does not provide enough power.  We (UtilityBee and robo_donut) had tried to replace the supply for an oldish Dell XPS with a generic Gateway supply when we stumbled into this problem.  Hopefully the notes we provide will prove useful to others.  Note that the following hack forces the supply to register regardless of whether it actually satisfies the power requirements or not.  You must choose your supply carefully and, if you attempt this, you do so at your own risk.

The Dell power supply contains a single IC in a TO-92 package labelled "DS2501".  Some research turned up a forum post which explains that this chip is a one-wire EEPROM containing information about the supply.  No comprehensive datasheet seems to exist for this part.  We found some speculation that the DS2501 might be a lower capacity version of the DS2502, for which there is a datasheet available.  The IC has only two connections, one for data and one for ground.  The device is powered through the data pin using an internal diode and capacitor to obtain and store power.

In order for this trick to work, this chip must be in good working order.  If your laptop fails to recognize your current supply as an official Dell supply (i.e. it gives you a warning during POST), then this chip is bad and you cannot salvage it.  If the supply is dead, but the laptop gives no indication that the supply is incompatible, then there's a good chance this chip still works.

First the original Dell cable must be salvaged, along with this IC.  The ground of this cable should be connect to the ground of the new supply and the positive voltage out must be connected to the positive on the new supply.  It is left up to the reader to correctly identify these wires (ground should generally be on the outside).  The data is a small pin in the center of the connector and the wire runs down the middle of the cable.  The middle (data) pin of the DS2501 should be soldered to this data wire, and the ground should be soldered to the cable ground (pinouts for the IC are listed in the datasheet above).  That's all there is to it.  Insulate all the wires, test the new supply, and add any finishing touches.