Have a few days off for the holidays which allows me to get some of the more tedious work done.
I mapped out the complete MIDI EDAC connector to the main board. It includes signals for an RS232 port and two foot switches.
I also rebuild the Metronome level pot. It was jerry-rigged with a resistor and a capacitor and both were broken. This one was also soldered to the connector on the main board, which makes removing the main board a bit harder. So I rewired it, with a connector and now it can just plug in. As a result, the speaker / buzzer is audible again (without the pot, the volume was at the lowest, barely audible).
The IDC for the memory card has been mapped out pretty much as well, so I can get started on building something for an EPROM. This is going to be a nice little gig, as I do have an EPROM emulator, so I can use that to hopefully experiment a bit to make it work.
Right now I have this one:
But the guy who built the CPU emulators also has some kind of EPROM emulator based on a teensy, so these may be interesting as well:
https://github.com/MicroCoreLabs/Projects/tree/master/EPROM_Emulator
In terms of hardware, it looks like the machine is pretty much done. Except for the stereo audio part (which, as far as I can see from various videos / photo’s Vangelis did not use), but the replacement pots are on order and I’d need to build a breakout box for that as well. It’s not a priority. I got a 19inch enclosure to build the MIDI breakout box, but the front panel is WAY too thick. Going to see if I can find a practical alternative soon. I have the 40 lead cable, enough sturdy DIN sockets, so once I get with Paul to confirm my findings, I can start building that.
Below are some screenshots from the mapping of the various connectors. This is also part of the documentation I’m creating on the hardware. Original schematics were most likely lost (although Vangelis had copies of everything, when they needed it in 2007 it was no where to be found – perhaps they find it at some point…one can always hope…).
In essence, the system’s hardware isn’t that spectacular – it’s just basically a M68000 CPU with a bunch of memory and 5 DUARTS (and a sh*tload of TTL). Which is good, because there is nothing custom in there. But it is clearly a prototype as it has literally over 40 jumper wires on the back of the PCB. It’s the software part that is the tricky part. I’ll elaborate more on that on another post in a few days.
Happy holidays!
