Control/Dimming - Lightboard M

[waynehoskins]

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.

[Footer]

I doubt anyone here will be able to help you, and if they can more power to them and you. If you are just doing this for a learning experience, could be an interesting one. My approach would probably be to convert the AMX to DMX, and build that converter. Who knows what is on that header, in the 80's nothing was standard, not even the connections inside the box. Might be interesting to hook up a scope to the header and see what it does when you mess with stuff on the console, thats probably going to be your best bet.

[SHARYNF]

THere were two models of this board, one with wooden sides, and one with grey metal sides, my undestanding is that the metal version had a option for dmx. I happen to have two of the wooden sides versions, I have just used a convert to go from amx to dmx.
Sharyn

[waynehoskins]

Cool, this is the first generation, the wooden-sides one.

I ought to just get a Pathway or Grey or whoever converter anyhow, to put in the Get Me Out of Trouble box. (Or figure out how to build one myself, but that's a small undertaking, demuxing and A/Ding the AMX into bytes and stuffing those into memory locations and then looping over the memory to give data to a UART to make DMX)

[TimMiller]

i picked up an ETC AMX to DMX/DMX to AMX converter on e-bay a while back for about 50 bucks. I know gear source has some for around 200 or so.

[waynehoskins]

Originally Posted by TimMiller

i picked up an ETC AMX to DMX/DMX to AMX converter on e-bay a while back for about 50 bucks. I know gear source has some for around 200 or so.

Hmm, I'll have to drive over there .. well, not in the literal physical sense; I mean drive my web browser over there. I had been watching consoles on them and some of the others for a while, but I hadn't thought of looking there for protocol converters too.