I have two right arms, and I think that you are possibly having the problem because of confusion on how to place the
instrument (Source 4) on the bracket.
The bracket will always home in the same place, however, there are several adjustments as to how the bracket sits on the drive post. The trick is to adjust how the bracket sits on the drive post, and the tilt of the bracket, while also adjusting the tilt of the
instrument, until you have the
instrument in the position you want it to be at the extreme limit when the
console is sending 0%.
It is important to find the center of gravity of the
instrument with its's various options, such as
scroller and or
iris. once you know the center of gravity of the
instrument. you want to place that as close to the drive post, by adjusting how the bracket is positioned on that post. (This is a very large
nut that allows the bracket to slide up and down in relation to the post.) In conjunction with this adjustment there is a tilt adjustment at the top of the bracket. The tilt of the
instrument is also figured into this balance.
It is best to do these adjustments when the
right arm is not powered, so that you are not forcing any movements against the stepper motors. Once you have the
instrument where you think that is both in the starting or home position, and it is balanced, take your hands off of it and it should not move. Now try manually moving it up and down and again it should stay where you place it, or a very slight position change.
All of this is with the
power off. Now apply
power and
send it some
DMX. Depending on if you are sending it regular
fader signals, or
encoder signals, It should home at one end of the travel, or center in the case of an
encoder. Depending on how much travel you want it to do, you can proportion your
dimmer in the patch of the board, and give better resolution to travel movement.
The balance and homing position are something that you might have to try several times until it works just as you want it. Once you have one of the units as you like it, measure the bracket and
instrument positions and repeat them on any additional right arms of the same setup.
As for the
iris staying in the
instrument, you can always move the
iris cover on the
instrument to partially
cover the
iris and tighten the two screws. If this doesn't work, remove the
iris cover, get some longer screws, (8-32x1inch) at Lowes or home depot. Put the longer screws into the holes for the
cover and tighten until they touch the
iris housing inside the
shutter assembly. Tighten only as much as neccesary to keep the
iris from moving. Over tightening could possibly damage the
iris.
Tom Johnson