The PSU on the MEK6800D2 is a bit of an unknown quantity and built on veroboard. The whole assembly really isn’t in keeping with the rest of the system. I did find out that new LM309K’s go for near on $100 though! (the old PSU has one)


So I’m taking the opportunity to build a new power supply. Still using a TO-3 style metal-can regulator, and a TO-3 SCR to crowbar the PSU in case of an overvoltage condition (sooner blow a fuse than blow up the 6800 system). I could have used modern packages, but I wanted to stay at least a little retro :-)

The new one looks kinda, sorta, like this. There’s a heatsink for the regulator going where the white box is. The SCR (top left) shouldn’t need one – it’s doing nothing unless the PSU has gone into over-voltage, and only then for long enough to pop the fuse.