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128/512/Plus 240 V PSU Schematics

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.

Screen Shot 2021-09-08 at 22.18.36.png
Input, rectification and filtering.


Screen Shot 2021-09-08 at 22.07.09.png
Feedback control circuit


Screen Shot 2021-09-08 at 22.07.20.png
Switching converter core


Screen Shot 2021-09-08 at 22.07.28.png
Output and crowbar circuit

 

Attachments

  • 240V_PSU.pdf
    433.4 KB · Views: 7

Cinan

Well-known member
Yes I did and great work. I think my problem is back at Figure 2 of the original doc though re the horizontal sweep and high voltage circuit.
 

michimartini

New member
Thanks for your effort - it inspired me to redraw it in Kicad. And in doing so I caught a few errors in your drawing as well.
Attached is an archive of my kicad project in case someone wants to improve on it and then there's a color and a b&w PDF of the schematic exported from Kicad. There are also two PNGs that are annotated versions of your handdrawn schematics where i point out where you got it wrong.
 

Attachments

  • macintosh-power-circuit-240v.zip
    138 KB · Views: 6
  • macintosh-power-circuit-240v-bw.pdf
    62.8 KB · Views: 5
  • macintosh-power-circuit-240v-color.pdf
    63.2 KB · Views: 2
  • 240v_psu.png
    240v_psu.png
    144.5 KB · Views: 7
  • 240v_psu_error_amp.png
    240v_psu_error_amp.png
    49.6 KB · Views: 7

cheesestraws

Well-known member
Thanks for your effort - it inspired me to redraw it in Kicad. And in doing so I caught a few errors in your drawing as well.

Oh, wonderful. And thankyou for your corrections, also—I was really hoping someone would double-check me—I'm surprised I didn't get more wrong than that!
 

michimartini

New member
Sorry, there was an error: C22 was a duplicate of C34. Fixed in this version.
 

Attachments

  • macintosh-power-circuit-240v.pdf
    63 KB · Views: 1

michimartini

New member
That would be great. Here is the complete archive again - now with the C22 fix included. The uncluttered version is without the dotted lines.
 

Attachments

  • macintosh-power-circuit-240v.zip
    631.7 KB · Views: 6
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