Mac 512k with Arcturus RAM & SCSI upgrade

Nov 4, 2021
136
112
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Tucson, AZ
I picked up a Mac 512k with a Rodime external hard drive. Initial fire up hooked hopeful; it made a happy beep but the screen didn't turn on unless I smacked it on the side. Cracked solder joints, easy-peasy, so I ordered the recap kit and long torx bit from Console 5. Once those parts came in I cracked the machine open and found a mysterious set of PCBs, perf boards, and lots of bodge wires.
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My Google-fu didn't turn up any mention of this addon, but it kinda looks like a clone/home brew version of a Mac’s-a-Million.

The perf board, bodge wire, and square dupont pins soldered to the outside of the CPU pins is certainly a choice.
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Unfortunately I jiggled the wrong bodge wire while recapping so now I have to figure out why the video is garbled, but at least the CRT powers right up now.

Has anyone seen one of these before?
 

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Builde68

New Tinkerer
Oct 19, 2025
9
1
3
It looks more like a stripped-down MacSnap RAM expansion board. It doesn't seem to have any 74xx logic chips or PLDs besides the RAM ICs and the pair of 74244s, right? It looks like a homebrew 512KB RAM expansion prototype. To expand just 512KB, it doesn't need any additional logic. Could you show more pictures of the SCSI interface, without the ribbon cable installed?. It should have at least a resistor and a capacitor that together form an RC timing circuit, in addition to the 74xx ICs.
 
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