Quoted from Robotworkshop:
Supposedly if the AV board is dead you can use a WPC DMD driver board and then a separate sound card like the Pinsound or Tilt Audio.
well ... let's say rather that it is not exactly TRUE
But this need some technical explanations...
Indeed, many people think that the WPC-95 (A-20516) Audio Video board can be replaced with a separate video board from WPC-89 / WPC-S (A-14039) and an independent audio board (like Tilt Audio, or Pinsound).
Granted, it works in some cases. But not always! Why?
➤ Simply because it's not exactly equivalent to an original WPC-95 AV board.
Let us not forget either the serial interface (which is independent of the ASIC), which is lost if one replaces an AV card by other boards. Granted, this was only used on the "NBA Fastbreak" and "Phantom Haus", and isn't really something essential, except if you want to play NBA in network, or connect the serial printer.
Remember that, no one has ever seen the ASIC datasheet used on WPC-95 AV boards and it is only "assumed", or "presumed" to be identical to the discrete components previously used on WPC-89 / WPC-S board. However, this assumption is a mistake , because Williams made some improvements by creating this ASIC, with features that are not found on previous WPC-89/WPC-S boards.
Really ? YES.
A simple example: if you look at the diagram of the DMD WPC / WPC-S video board (A-14039 or A-14039.1) you will see that this board will never be able to manage DOT displays of more than 32 lines. Indeed, the comparator (U21 - 74HC588) receives only 5 address lines and on the other hand, the hardware generation (U23A / B / C + U6C / D) of the synchro signal (ROW_DATA) also only uses 5 bits.
However, there is a WPC-95 machine with a display of more than 32 lines: the "Phantom Haus", which has a 128x64 DMD - in other words, 64 lines!
So how can this work?
⬥ I disassembled the part of the ROMs concerning display management and the obvious: the registers in the ASIC are more than 5 bits, since sometimes a value greater than 32 is written in them. Without going into too much detail, let's say the bottom line is that the ASIC registers on the WPC-95 AV board are a bit different from those implemented on the WPC-89 / WPC-S video board.
Moral: The video section of a WPC-95 is well designed differently from that of a WPC-S, although at first glance it looks similar.
⬥ I had already made this observation by analyzing the ROMs of certain pinball machines, produced both in WPC-S and in WPC-95. Because there are indeed some VERY particular models in the WPC-S and WPC-95:
- the "Demolition Man", which is a WPC-89, but which also served as a prototype for the WPC-S
- the "Jackbot", which is a WPC-S, and which served as a prototype for the WPC-95
- the "Phantom Haus", which is a WPC-95 with very specific hardware and a larger resolution display.
- the "Congo", originally produced in WPC-95, but which was then offered as a conversion kit for WPC-S (keeping the WPC-S boards)
For the latter, there are ROM versions that work just as well on a WPC-S CPU board as they do on a WPC-95 CPU board!
This is surprising, because the hardware (driver, audio, video) is obviously not the same at all.
When the CPU starts up, the video board registers are interrogated. The answer being different between a video board WPC-S A-14039 and an AV WPC-95 A-20516, it is thus possible to determine whether the pinball machine is a WPC-S or a WPC-95.
It goes without saying that this kind of functionality can never be integrated on an alternative audio card, since it is the video part of the ASIC which is used to make the identification.
It is not possible either, to use an AV board to keep the video part and to put another audio board next to it. Because the audio and video sections of ASIC are inseparable and cannot be deactivated. Connecting a second audio board, while leaving the AV board in place, will lead to conflicts (exchanges with the CPU being bi-directional).
And for those who haven't had the courage to read these technical explanations, let's summarize:
There are cases, where for a WPC-95, installing an alternative audio board (TiltAudio, Pinsound ...) does not work.
Having said that, TiltAudio is still a great project