Quoted from OlliG:Progress Update with my repair....
I have Sound AND Speech now !!! Yehaaa!!!
The problem was with the speech board. Pin 4 on the Op.Amps MC1458 did not get the -12V. The holes in the board of these chips are not connected through (from top to back side of the board. so if you solder the chip or socket from below.... the -12V arriving at the top side of the board are not reaching the pin...
So I had to solder the socket pin from above to...
Result: Loud and nice speech
To find this out drove me crasy... I never imagined that the upper and lower side of the board were not connected through!!!
Maybe my board is a faulty one... it is one of the old boards that dont have the jumper for the different Eprom types....
Last remaining problem is the socket of U14 that has to be redone.... I still sometimes have the freezes and the game would shut down...
If I slightly press on U14 it comes up again!...
Nice detective work. Your saving yourself a fortune by doing the work yourself, I'm jealous.