waynehoskins
Active Member
So an odd question, mostly for those of you who have been in the industry longer than I have.
The earlier Lightboard M (in this case, 1987 screened on the logic board) has an output driver card that's about five-by-six inches and attaches to the logic board with a 34-pin two-row header. In the case of the sample I have, it's an AMX driver card. Presumably they also made other (D54 in Europe) driver cards to go there. I've done a little bit of poking around on the board and found out some stuff about the driver card.
It takes an 8-bit data bus from the logic board and feeds that parallel into a pair of dual 8-bit D/A chips, the output of each channel of D/A feeding, with appropriate buffering and such, the analog line of one of the four AMX output jacks. The channel select and enable lines of the D/As are fed by some logic that switches the single data bus to the appropriate channel of D/A and output.
It also feeds a 10-bit counter back to the logic board.
It also picks off a couple of other signals from the logic board and feeds a couple back to it.
That's the result of maybe four hours of looking at the thing today and tracing traces.
What I'd like to do is fabricate a DMX driver card to go in place of the AMX card. Here come the questions...
- Has anybody done this before?
- Has anybody worked with the signals on that 34-pin header?
- I think the 10-bit counter is used as an address bus that requests a particular output address from the logic board. Anybody know if this is right, or if instead the logic board always sends values and the counter is only used as a watchdog type of counter?
Yeah, I know, 20-year-old board, ancient technology .. but I enjoy tinkering with stuff like this. Also a good excuse for me to learn how to do stuff the Old Way.
The earlier Lightboard M (in this case, 1987 screened on the logic board) has an output driver card that's about five-by-six inches and attaches to the logic board with a 34-pin two-row header. In the case of the sample I have, it's an AMX driver card. Presumably they also made other (D54 in Europe) driver cards to go there. I've done a little bit of poking around on the board and found out some stuff about the driver card.
It takes an 8-bit data bus from the logic board and feeds that parallel into a pair of dual 8-bit D/A chips, the output of each channel of D/A feeding, with appropriate buffering and such, the analog line of one of the four AMX output jacks. The channel select and enable lines of the D/As are fed by some logic that switches the single data bus to the appropriate channel of D/A and output.
It also feeds a 10-bit counter back to the logic board.
It also picks off a couple of other signals from the logic board and feeds a couple back to it.
That's the result of maybe four hours of looking at the thing today and tracing traces.
What I'd like to do is fabricate a DMX driver card to go in place of the AMX card. Here come the questions...
- Has anybody done this before?
- Has anybody worked with the signals on that 34-pin header?
- I think the 10-bit counter is used as an address bus that requests a particular output address from the logic board. Anybody know if this is right, or if instead the logic board always sends values and the counter is only used as a watchdog type of counter?
Yeah, I know, 20-year-old board, ancient technology .. but I enjoy tinkering with stuff like this. Also a good excuse for me to learn how to do stuff the Old Way.
