Control/Dimming Light Boards Compatible with CD80 Dimmer Rack

[pathway]

I installed several CD80AE racks in the 1990-93 timeframe and they definitely accepted DMX512. As I recall the screw terminal connectors were located at the top left side of the rack. Assuming your AMX192 connections are still there, I believe that you only need to reconnect DMX on the "Common", C+ (or D+) and C- (or D-) terminals (depending how they're labeled). If the data wiring is intact back to the control booth, you could probably just install a 5-pin male in place of the existing 4-pin, reusing everything but the red (analog mux) lead. I'm pretty sure the AE rack will auto-detect DMX512, but I may have to do a little more research if this advice isn't sufficient.

 

[DimmerDotCom]

I installed several CD80AE racks in the 1990-93 timeframe and they definitely accepted DMX512. As I recall the screw terminal connectors were located at the top left side of the rack. Assuming your AMX192 connections are still there, I believe that you only need to reconnect DMX on the "Common", C+ (or D+) and C- (or D-) terminals (depending how they're labeled). If the data wiring is intact back to the control booth, you could probably just install a 5-pin male in place of the existing 4-pin, reusing everything but the red (analog mux) lead. I'm pretty sure the AE rack will auto-detect DMX512, but I may have to do a little more research if this advice isn't sufficient.

Sorry to resurrect an old thread. On AE that was input protocol setting "0". Sometimes we hard programmed the Input Processor using the HHR to either be AMX or DMX as sometimes the "0" setting would cause flakiness as to what it was locking in to.

 

[FMEng]

I installed several CD80AE racks in the 1990-93 timeframe and they definitely accepted DMX512. As I recall the screw terminal connectors were located at the top left side of the rack. Assuming your AMX192 connections are still there, I believe that you only need to reconnect DMX on the "Common", C+ (or D+) and C- (or D-) terminals (depending how they're labeled). If the data wiring is intact back to the control booth, you could probably just install a 5-pin male in place of the existing 4-pin, reusing everything but the red (analog mux) lead. I'm pretty sure the AE rack will auto-detect DMX512, but I may have to do a little more research if this advice isn't sufficient.

Well, almost. The type of cable for AMX192 is probably not the correct impedance for DMX. It needs to be twisted pair with 120 ohm impedance. If it's wrong, it might work some of the time, and drive you crazy with weird glitches. I have no idea what the characteristics for AMX would be.

 

[pathway]

Regarding cable impedances for AMX and DMX, you can pretty much interchange them with no issues. AMX protocol was based on the RS-422 standard (485 didn't appear till a few years later) and that spec'd 100-ohm cable. Common examples are Belden 9729 and 9829. 9729 is always fun because it has a black-red pair and a black-white pair, making it super easy to miswire the blacks. The clock pair (C+/C-) is a differential signal so it needs to be on a twisted pair. Common and analog-mux use the other pair and having common wrapped together with the analog signal can't hurt either.

DMX512 is based on RS-485 (now called EIA485) which uses 120-ohm cable. The 20-ohm difference is pretty much insignificant for signals crawling along at 250K Baud, which is 1/40th the maximum design speed for EIA485. This is why you'll find 100-ohm cable used interchangeably with 120-ohm in old and new installations. And Cat5/6 cable, which is being used more and more for DMX, is also 100-ohm.

Bottom line -- if you can re-use your AMX cable for DMX512, go for it. But first try to find the cable's type# and look it up online to make sure the installer at least used proper 100-120 ohm data cable rather than audio cable.