The colour SE/30 - including making an ATX to Macintosh SE/30 power cable.

Inspired by Mac84 and others, I had been working on the different parts of building my own colour SE/30…

Step one was getting my Lapis ColorServer PDS/30-17 working. The supplemental VRAM modules brought it back to life! So, it wasn’t that the existing ones were faulty, it was that the replacement ROM I had burnt was for a model of card that expected more VRAM than mine. Good to have diagnosed the issue correctly and have that now working happily.

The next piece of the puzzle was building a custom power cable to directly supply the main logic-board the inputs it requires. Within a typical SE/30, the mains power goes to the analogue board which powers the internal CRT as well as then powering the main logic-board. With the setup I was working on, the display would be connected through the Lapis card, so I could thankfully leave off the 30+ year old power supply and CRT and replace the former with a relatively new ATX power supply (this is the typical PC desktop type power supply). The only voltage rail missing is the -5V, which did in fact used to be part of the ATX specification. To get around that I found a project on Tindie which uses a voltage regulator to add that power rail back in. I also ordered an ATX extension cable, an inline power switch that connects the ATX pins that tell the power supply to switch on and off, the smaller Molex Mini-Fit Jr. connector that most of the compact Macintoshes used for the main logic board power (AKA the “J12” connector), and a small form factor ATX power supply. Finally everything was assembled this week, I removed every wire from the ATX power extension, cross referenced the pins, inserted just the necessary pins/wires, double-checked all the voltages and ran through the first test of connecting everything (AKA the “smoke test”).

Success! I can now run this machine quietly and safely on my workbench, in glorious colour :)

Currently listening: Urban Flavour - Modern Jazz Drum n Bass (1998)

Jonathan Wrigley @workswellforme