Does anyone have a Gamatron set up with a VSU-100? Sure, I hope so - because I have the thing nobody asked for!
A custom sound rom with "blast" "off" replaced with "gama" "tron"

Caveat: it requires a second rom chip in U10 to hold the extra samples. f2k normally only requires one.
Bonus: the sample phonemes/diphones? came from Orbitor 1

Extra caveat - it's untested! Does anyone want to be a guinea pig????

Full word table extracted to a WAV file, check it out! https://ef9a.com/f2k/f2kgama.wav

U9 + U10 images: https://ef9a.com/f2k/f2kgama.zip

It should be able to be tested in a f2k. I just don't have a spare rom or burner to do so myself
the obvious issue I think we'll run into is that the words have a different number of letters, so it is basically guaranteed to play them at them at the wrong time when spelling. Though it should be OK when launching multiball.

That is a good question. I don't know enough about the pinstar board to give a good answer!

So - I've been looking into this, and found an old forum post by you Chosen_S !
Where are you at in this process? Is it just the J3 connector?

It's been 5 months, but I can finally confirm that it can speak! Thanks to some help from gamatron2000 and generous use of a machine from drgnlair .

How much work is involved depends on the MPU board used with the conversion kit.

J1+J2 are straightforward since they just pass through the connection from MPU to lamp matrix.
J3 requires 4 connections (double check the connections for your specific game just in case!).

• J3-1: General illumination. The obvious choice was to tack this onto the hot side of the GI lamps which power the backbox.
• J3-2: Key, no connection

• J3-3: Voice out. This normally goes to J3-5 on the SB-300 sound board. On the Pinstar board, this pin is probably not connected to anything. It needs to connect somewhere on the junction of C14 and R23. Of course, Pinstar decided their board did not need a silkscreen , so these parts are unlabeled. See the photo for how we ran the green jumper on the backside.
  Voice Input
  Pinstar Jumper Location
• J3-4: Lamp Strobe 2. Goes to J1-8 on the MPU, and with any luck it is not used! Just crimp a pin on the wire and slide it in.
• J3-5: Lamp Interrupt. This is normally J4-11 on a MPU-200. On MPU-100 and Bally AS-2518 based boards, this does not connect to J4!. Instead of pulling the board out to run a jumper we soldered a wire to the high side of R24. Yeah it's not a great solution, don't flame too hard in the comments.
  LOL

Honestly, the hardest part might actually be obtaining a working speech board. We built a custom replacement, the VSU-2 (for sale soon??).
VSU-2

Chosen_S - We made a batch. Careful what you wish for!
https://pinside.com/pinball/forum/topic/new-replacement-for-vsu-100-speech-board