cheesestraws
Well-known member
I know a number of folks have been here wrangling 240V Pluses/512s/128s recently, myself included.
Schematics for the 120 V version of the power supply are reasonably available, notably in Thomas H. Lee’s commentary on the design. However, the 240V version is laid out differently enough to be disorientating, and the component designations are totally different, and schematics do not seem to exist. So I spent a couple of afternoons drawing them out, more or less, and I offer them here for people's edification and delight.
Fortunately, the 240 V PSU is extremely similar (perhaps unsurprisingly) to the 120 V one, so I have laid out the schematics and split them up in the same way that they are split up in the document linked above; that way, the text and diagrams in that document should be able to act as a guide to roughly what the 240 V one is doing, also. Figure numbers in my schematics correspond to figure numbers in that document and cover the same parts of the circuit.
Note, please, though, that I do not wrangle power supplies professionally, nor am I strictly speaking within my comfort zone here. I have checked this information twice, but please verify anything important yourself with measurements on your own board if in doubt.
Images are here: PDF is attached at the bottom of the post, or at the semi-stable URL https://windswept.home.blog/2021/09/08/macintosh-128k-512k-plus-240-v-power-supply-schematics/
Please feel free to copy, save, archive and distribute as helpful.
Schematics for the 120 V version of the power supply are reasonably available, notably in Thomas H. Lee’s commentary on the design. However, the 240V version is laid out differently enough to be disorientating, and the component designations are totally different, and schematics do not seem to exist. So I spent a couple of afternoons drawing them out, more or less, and I offer them here for people's edification and delight.
Fortunately, the 240 V PSU is extremely similar (perhaps unsurprisingly) to the 120 V one, so I have laid out the schematics and split them up in the same way that they are split up in the document linked above; that way, the text and diagrams in that document should be able to act as a guide to roughly what the 240 V one is doing, also. Figure numbers in my schematics correspond to figure numbers in that document and cover the same parts of the circuit.
Note, please, though, that I do not wrangle power supplies professionally, nor am I strictly speaking within my comfort zone here. I have checked this information twice, but please verify anything important yourself with measurements on your own board if in doubt.
Images are here: PDF is attached at the bottom of the post, or at the semi-stable URL https://windswept.home.blog/2021/09/08/macintosh-128k-512k-plus-240-v-power-supply-schematics/
Please feel free to copy, save, archive and distribute as helpful.