Macintosh 128k/512k/Plus 240 V Power Supply Schematics

The early Macintosh computers, the 128k, 512k and Plus, can have one of two different analogue boards, which contains the CRT circuitry and the power supply. One of these versions is for 120 V supply in the US; the other is for 240 V (ish) supply elsewhere. In theory, the 240 V one can also be configured to work on a 120 V supply.

Schematics for the 120 V version of the power supply are reasonably available, notably in Thomas H. Lee’s commentary on the design, here:

However, schematics for the 240 V PSU have been less forthcoming, so I traced them out. This PSU turns out to be very similar to the 120 V one, to the extent that I have structured the schematics after the schematics in Thomas H. Lee’s document, and split it up in the same way.

The figure numbers in the schematic PDF correspond to figure numbers in the earlier document and cross-referenced, the two form a guide to the 240 V PSU as well.

Here they are:

Author: Rob Mitchelmore

I don't believe in bios.

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