Wednesday 9 December 2009

Home made Mac LC to VGA video cable

I still haven't got around to fixing the heating in my car. It's looking like a lot of time and effort and I can live with it the way it is for a while longer. In the meantime I've had some other projects on the go. I've been clearing out lots of old junk and giving most of it away. One of these is a 266 MHz G3 PowerMac desktop model dating from 1997 which had once belonged to my wife. Because I'm consciencious, I wanted to make sure it's up and running before giving it away. The problem was that it has the old LC15 video output and I don't have an old Mac monitor, nor do I have a suitable VGA adapter. Since this is a freebie job, I also don't really want to buy one. So I decided to make one. I found a lot of good info on the web and particularly followed the advice given here:

I also checked wikipedia for the pinouts of the VGA HD12 connector. The article for that is here:

I'm ashamed to say it took me a couple hours to make the cable. This is partly because I had to tear old cables apart and it took some time to find a suitable DB15 connector. Partly because the soldering was a bit fiddly. In the end I used an old game port MIDI interface cable end and that worked nicely. To be honest I wasn't confident the thing would actually work, but it did. I can get up to 1024x768 resolution on my 17" LCD display supposedly with thousands of colours; however, only the green signal is coming through. That might be because pins 5-8 on the VGA side appear to be wired to common ground and so I couldn't wire up separate grounds for the colour channels like the diagram suggests. Maybe later I'll see if I can get the VGA connector apart and change the wiring on it. On the other hand something may just have come loose or made improper contact when I packed the wiring inside the end. For now though the result is good enough to setup a new larger hard drive and install the system and other software.


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