The pushbutton switches on the DMX and DX often become intermittent in operation after some time. You can correct this problem in some cases by careful cleaning.
New: Switch cleaning video demo available here.
To clean the switches, you will need to remove the switch caps. I strongly recommend removing the front panel board from the case for easiest access to the switches. If you have only one or two switches to clean, you may be able to get by without removing the front panel printed circuit board first, but this is dangerous because it is very easy to accidentally damage the switch while trying to remove the cap this way.
Mark the switches that need cleaning by putting pieces of tape on the switch caps.
To remove the front panel printed circuit board:
To remove the switch cap:
Use the flat blade screwdriver to carefully pry the switch cap off with a lever action, alternating from one side of the switch to the other. Be sure to lever the screwdriver only between the switch cap and the switch body, not between the circuit board and the switch. You should feel a "pop" as each of two posts come loose, and the cap should then come off easily.
The switch operates when the contact wire which goes across the top of the coil spring is allowed to touch the stationary contact wire. The switch cap only presses down on the coil spring and doesn't touch the contact wires directly.
Once the cap has been removed, blow out any accumulated dust, and spray some contact cleaner on the point of contact between the two switch wires. You may want to reconnect the ribbon cables at this point, and set the front panel PCB on a piece of cardboard to insulate it from the voice boards and the main circuit board. Reconnect the power and turn on the DMX to test the buttons now. If the contact cleaner worked, you can stop now.
If the switches are still intermittent, carefully scrape the oxidation from the contact wires at the point of contact, using the X-acto knife. Scrape the underside of the upper wire, and the top of the lower wire. Be careful to scrape gently, and don't nick the wire. Do not deform or move the contact wires out of place.
When all the switches are clean, disconnect the power again, and reassemble the DMX.