After repairing a lot of these early bally soundcards:
The AS-2518-32/50
I decided to built a new one from scratch.
This time I want to do it right...(not with a breadboard construction)
Here you see my layout:
I altered the orignal design in the following way:
Power supply:
I changed the power supply part for the + 12 V. The + 43 solenoid power is not longer needed.
Bally used in newer soundcards the existing unreg 12 + with a filter cap:
This means, that you have to add a wire to your pinball, (but then you can swap between the sound50 and the existing soundcard...)
U3 Prom:
I want to replace the U3 (82s123) prom.
This prom has a very fast access time (50 ns), so it was not possible to replace it with an 2716 eprom (access time > 200 ns)...
There is a solution for this, this chip is called GAL. This is a (custom) reprogrammable logic device. For the entire information of the 82s123 (a total of 32 bytes...) you need a gal22v10 chip.
Here is the libary for your eprom burner (my needham-20 supports this chip whitout any adapters)...galu3.zip
Use T18.JED for the following pinballs:
Lost World, 6 Million Dollar Man, Playboy, Supersonic, Star Trek und Kiss
Use T51.JED for the following pinballs:
Paragon, Harlem Globetrotter, Dolly Parton
You still can use the orginal 82s123 prom (I added an additional socket for the gal...).
The sound50 card is much smaller in the physical dimensions (8 cm * 10 cm -> 3 inch * 3.9 inch) because:
- the power supply is gone...(no need for a tip29c and a large heatsink or a 5w resistor...)
- I used the smallest caps availiable..
There are only three jumpers on the board: For use in the following pinballs:
Lost World, 6 Million Dollar Man, Playboy, Supersonic, Star Trek und Kiss
Add jumper R103 and R102. Remove R101.
For use in the following pinballs:
Paragon, Harlem Globetrotter, Dolly Parton
Add jumper R101. Remove R103 and R102.
Here you can download the schema from sound50 and the partlist.
sound50schema.zip
Caps are mounted...
Resistors are mounted...
Ehm...well, it was my first try with a layout software...I did some connections wrong...
Here you see the board with a 82s123 / -51 Prom
Here you see the same board with the gal chip (t51 Image)
The board is now working on my testbench...
Next I will mount the board in my pinball and make a longer test and document the process of adding a wire to my harlem globetrotter...
And I still have to test the -18 gal version...
Problems I have until now:
I still have to much noise. I think I created unwanted ground loops. I will try a better OP-Amp (TL071) and I will make eventually a new pcb.
Mail me