Re: DMX Problem
The local high school (and until a few years ago, the university) had MD288 racks driven by Express-series consoles with no problem, so it's not an intrinsic design flaw of the firing cards in the rack not being to make sense of Expression-era DMX512 (though there is a generation gap there).
You might consider, though, lowering your address count (dimmer count). I don't know if that would make a difference with the refresh rate, but it might stand a chance.
And then it could be just a sloppy RS-485 driver in the board that the opto cleans up for you. Could also be that the RS-485 line you're talking into has too much load (double terminated or too many devices) for the driver chip in the board, but the opto's outputs have a higher-current driver behind them.
In any event, if you can run the board directly into the rack, you should have no problems; if they persist, I'd really suspect the RS-485 transmitter circuit in the board (probably the oscillator if I had to make a WAG).
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