Ok. So you want to try to get it working in the original system. That was the information i was missing, i thought you wanted it to run in another system.
We can have 2 problems.
First the sound card does not make sounds.
Second the mixer is not set up properly to enable the soundcard input.

If you can you should verify that the sound card outputs something into the mixer.
You can either try to listen to the soundcard via a selfmade cable adapter, or you can try to input sound into the mixer via the cable from the soundcard..

Here i have made a utility package for your card.
Just copy the MMpro16 folder from the zip to your c drive and add the lines from the included autoexec.bat and config.sys to your autoexec.bat and config.sys (not just overwrite them, add the lines).
in the utility folder inside mmpro16 yo will find some programs to set up your card. SETMODE.exe can switch between Windows sound system and soundblaster emulation. CONFIG.exe let you set up ports and adresses.
DIAGNOSE.exe let you test the fm synthesizer, 8 and 16 bit sound output and midi(wich will do nothing until something is connected via midi).

DerBaum wrote on 2023-09-14, 12:53:

Ok. So you want to try to get it working in the original system. That was the information i was missing, i thought you wanted it […]
Show full quote

Ok. So you want to try to get it working in the original system. That was the information i was missing, i thought you wanted it to run in another system.
We can have 2 problems.
First the sound card does not make sounds.
Second the mixer is not set up properly to enable the soundcard input.

If you can you should verify that the sound card outputs something into the mixer.
You can either try to listen to the soundcard via a selfmade cable adapter, or you can try to input sound into the mixer via the cable from the soundcard..

Here i have made a utility package for your card.
Just copy the MMpro16 folder from the zip to your c drive and add the lines from the included autoexec.bat and config.sys to your autoexec.bat and config.sys (not just overwrite them, add the lines).
in the utility folder inside mmpro16 yo will find some programs to set up your card. SETMODE.exe can switch between Windows sound system and soundblaster emulation. CONFIG.exe let you set up ports and adresses.
DIAGNOSE.exe let you test the fm synthesizer, 8 and 16 bit sound output and midi(wich will do nothing until something is connected via midi).
panasonic_aztech.rar

Thank you!
The utility package you made seems to load properly at boot, but I still got no sound when using DIAGNOSE.EXE. I have taken a few pictures of the connection between the sound card and the internal mixer.

Edit:

If this is the correct output pinout for CN7 of a Sound Blaster 16 CT2230, then the issue could lie with the mixer, as I have no sound through the internal connection. If I route SB16 -> Ext Line Out -> 3.5mm input jack on the back of the PC (connected directly to internal mixer) -> Mixer, then I get sound out of it.

download/file.php?id=47099&mode=view

I can only guess at this point.
The mixer seems to have a data connection to the mainboard (the cable with the 5 seperate wires from the mixer to the mainboard).
I can imagine that it has to be switched from TV mode to PC mode or something like that. So that both sources dont play at the same time.
I have no idea how this could be done. The mixer could have a serial or a USB connection, or use any protocol they like. The switching will probably need some kind of initialisation software for the mixer.
You should really try to get the software it was shipped with.

I have some hardware too wich will do exactly nothing without a driver that initialises the thing... and i have no drivers...

DerBaum wrote on 2023-09-16, 09:23:

I can only guess at this point. The mixer seems to have a data connection to the mainboard (the cable with the 5 seperate wires […]
Show full quote

I can only guess at this point.
The mixer seems to have a data connection to the mainboard (the cable with the 5 seperate wires from the mixer to the mainboard).
I can imagine that it has to be switched from TV mode to PC mode or something like that. So that both sources dont play at the same time.
I have no idea how this could be done. The mixer could have a serial or a USB connection, or use any protocol they like. The switching will probably need some kind of initialisation software for the mixer.
You should really try to get the software it was shipped with.

I have some hardware too wich will do exactly nothing without a driver that initialises the thing... and i have no drivers...

I guess so…
Thank you for your help. One last question: do you know where to find the same connector for external line out? I would like to mount it to the unpopulated pads on the back of the board.

Paradoxpm wrote on 2023-09-17, 02:57:

...do you know where to find the same connector for external line out? I would like to mount it to the unpopulated pads on the back of the board.

(Example. Just look for the same type of connector at a local/cheaper source.)
https://cityelectronics.pk/product/audio-jack-pcb-mount/
This should be the type, where all pins are in a row. You maybe have to cut the small black centering pins on the bottom.
All connectors i can find have the centering pins, but your pcb doesnt have the centering holes.