Pla yin g wit h PSU

Getting into the power conversion case

1 Remove power supply

Take off the rear panel of the Lisa by undoing the two thumb screws at the top. The PSU is in the metal case on the right side. There’s another thumb screw at the bottom of the PSU attaching it to the chassis. Undo this, then pull firmly to disconnect it from the motherboard socket and the PSU should slide free.

2 Undo AC connector

For a recently-connected Lisa, wait 48 hours to guarantee the large capacitors have discharged before you remove the outer cover. Undo the two screws holding the AC socket to the case. Inside, undo the nut that holds the ground connection to the case. Unplug the Molex connector from the circuit board.

3 Remove circuit board

There are eight Phillips screws holding the board onto the bottom panel of the case; make sure you get them all. You then have to undo the two flathead screws next to the main transformer. These are used to secure the large Schottky barrier diodes that convert the AC supply into a DC voltage.