LisaList2

The MPU131 PUJT is used in the Apple designed Lisa Power Supply (not used in the DataPower design).

Possible modern substitutes include the 2N6116 and 2N6027.

In this YouTube video, Fabio's NMI describes a simple two transistor circuit that he successfully used to replace the UJT used in the Apple Lisa PSU.

https://youtu.be/X96RIusQehw?t=299

Later in the video, he describes difficulties regarding the pinouts of the original Motorola UJT MPU-131, the replacement he found (the Digitron MPU131), and the 2N6027 still available (ca. 2026). Perhaps part of the issue is in decoding whether the datasheet is showing the top or bottom view of the part, but regardless, using a meter to double-check the pinout of the actual replacement is always advisable when substituting parts.