I was given a MD288 rack by a
theatre that had replace it with three
ETC sensor racks. The folks that had the Teatronics rack had what they said were quite a few problems and that it had caught fire at one time. When I got the rack home in my garage and disassembled it, I discovered that all of the problems were because of one procedure. While the rack has the capability of 288 dimmers in modules of 4 dimmers to a module, They didn't have that many dimmers, but had that many circuits in the
theatre. They would move the modules from slot to slot for different shows. This was their way of hard patching circuits to dimmers. The
rail guides that hold the modules are pop riveted to the sides. The rivets on the side supports of the cabinet have plenty of space to grab hold. The ones on the center sections do not have very much space to grab. The problem is that when the modules are removed and reinserted many times, they eventually shear off the rivets. When this happens the rails will
drop down and the modules won't connect properly. In the worst case scenerio, the module will short the
power "in" connectors creating quite a
pyro show. There is nothing wrong with Teatronics racks in electrical design, the problem is in the mechanical design.
Don't remove modules any more often than necessary, and tighten the heatsink screws on the
power components of the triggering
circuit cards from time to time, and the racks should last forever. If you have less than enough modules to fill the rack, start at the top and fill the rows accross as you work down. This is because each vertical row is on a different
phase, and the phases need to be balanced. Set the start addresses on the second and third card so that they start where the privious
dimmer count ends in the column to the left. I ended up with a lot of great dimmers for nothing except a little simple repair work.
