Mac 128k/512k/Plus Logic Board Cable to ATX (Video + Audio)

Mac 128k/512k/Plus Logic Board Cable to ATX (Video + Audio)

More information about the power and connectivity was requested, so here it is!

First, I am operating my power supply from a VARIAC on a ground isolated transformer. Occasionally this includes a dim bulb tester to spare untested machines from burning themselves out on first boot.

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After this rudimentary protection circuitry I have a regular old budget ATX power supply:
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This requires a modification to the sensing line, which I hard-wired to ground so that the power switch on the back of the ATX power supply turns it entirely on and off. This is a convenient reference to get started with a custom switch.

After that I have a custom power monitor connected to a remote relay. The remote relay turns the entire protection circuit on and is located next to the monitor as the mint-green circular button on the lower left:
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The outlet connects to a power bar and is basically the "output" plugs for this whole setup. The on/off switch will turn the monitor and supply voltage.

Finally, coming from the ATX adapter I described in my previous post, I have these three additional cables which I connect the RGBtoHDMI to:
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These are the connections from the logic board to the RGBtoHDMI:
  • Red "V-Sync" from Logicboard to RGBtoHDMI Vertical Sync
  • Green "H-Sync" from logicboard to RGBtoHDMI Horizontal Sync
  • Gray "Video" from logicboard to "Green 2" on the RGBtoHDMI but you can use any color channel if you configure your RGBtoHDMI accordingly.
This is the RGBtoHDMI profile I created for compact macs. This will work on the following machines:
  • Macintosh 128k
  • Macintosh 512k
  • Macintosh Plus
  • Macintosh SE
Code:
sampling=1,1,1,1,1,1,1,0,0,0,5,0,0,0,0,0,0,1,0,0,100,256,100,256,100,256,0,256
geometry=172,22,512,342,512,342,2,2,0,1,15667200,704,5000,370,1,0,0
palette=Tea1002
output_colour=1
output_invert=1
scanlines=1
scanline_level=0

I have this saved in my RGBtoHDMI SD card as "Mac_Plus.txt" and it is the only profile (I removed all others) in the following path:
SD Card > Saved_Profiles > 6-12_BIT_RGB > Mac_Plus.txt