As my recently purchased console was in bits for some surgery (a lonely 4116 VDP RAM died) and I had to wait for replacement 4164 RAM, I decided to build the speech synthesizer board into the console. I had come across this Mainbyte article (http://www.mainbyte....ch_console.html) but didn't like soldering all those wires to the I/O port and dismembering the speech board. I have come up with an alternative that is easy to build and easy to reverse if necessary.
Instead of just using the I/O port I used the cartridge connector. All necessary signals except 4 are available here and conveniently the pins for the cartridge connector have not been trimmed which allowed me to stick a custom connector on its back (see photo 1). I made this connector from a IC socket (the cheap ones, machined ones don't fit). I cut the rows to the required length, roughed the sides up, sparsely put superglue on 1 side, stuck this length on the back of the cartridge connector and then pushed the other length on. It's was a tight fit and after the glue had sufficiently dried it has become a solid connector. I then soldered a piece of flatcable onto my connector and sealed the thing with hot glue. The other side of the flatcable is soldered to a standard 44 pin S100 connector (Ebay). This connects up to the other side of the speech board.
4 signals coming in to the speech board from the console side are not carried through to the I/O connector on the other side: +5V, -5V, SBE* and AudioIn. All 4 are needed by the speech board so we need to connect pins 1,2,43 and 44 of both connectors (see photo 2)
To prepare the console for the speech board I glued (epoxy) 2 plastic standoffs to the top cover to secure one side of the board and its shield with 3mm screws. The other side of the speech board is held in place with Velcro (see photo 3).
You will need 4 signals from main board's I/O connector: SBE*, Reset* (the Reset line on the cartridge connector is active high so can't be used), Ready* and AudioIn. I used a separate piece of flatcable to solder to convenient points on the top side (just trace pins 1,2,43 and 44 and pick an easy spot to solder to). At the other end I soldered a standard 4 pin connector to connect up to its partner on the main flatcable (see photo 4).
Now it's just a matter of securing the speech board and shield (only the component side shield is used) to the top cover, route the flat cable into the cartridge connector cavity and replace the cartridge cover (mind the lip). You probably need to enlarge (a bit of filing) the slot for the cartridge connector if you have used hot glue to secure the custom connector (see photo 5).
If you have left enough slack in the flatcables putting together the console is still easy; the extra step is to insert the cartridge connector in its slot before securing the main board.
I used Thierry's site for the I/O and Cartridge pinout (see attached PDF for a reference). It's tricky to keep track of which top and bottom pins to use so check twice before soldering