Newport TRA motorized actuator, stepper version
(dirty optos?)
SYMPTOM: Motor hums, leadscrew doesn't move. Opto sensor not reporting "home",
step-motor runs then stalls at leadscrew physical end-stop.
OPENING THE UNIT: it's glued together with brittle glue, so squeeze each end of the stainless steel tube gently w/pliers, to crack the glue, grasp the tube, then turn each end w/pliers to crack it loose. Pull the cable-end partly out, then unplug the two tiny connectors.
The end-stop IR opto-sensors are found on a long green PCB. Remove this by scraping off the glue at multiple points using a razor-knife tip. Then pry up the board from either end GENTLY, using a tiny screwdriver to crack loose the glue.
I removed the three tiny allen-head (1/16") screws holding the motor assembly, then unsoldered the four step-motor leads, so the leadscrew can now be turned by rotating the entire motor.
POSSIBLE FAIL: The reflective sensors might be getting fooled. Inside the brass leadscrew assembly, the rotating slotted cylinder is filthy! (The sensors need a clear view of the reflective steel surface.) The surface had multiple large stains, perhaps some sort of hardened grease w/apparent rust. It dissolves with IPA alcohol. So, I thoroughly cleaned the sections under the opto-sensors w/sharp Q-tips, rotating the whole motor.
TO SLIGHTLY ROTATE THE LEADSCREW: the step motor has a 1:256 gear-drive module. You can slooooowly rotate the leadscrew by pushing a piece of heat-shrink tubing onto the small shaft-disk at the back of the tepper motor, then spin the tubing w/fingers.
Internal wire colors
- BK BR OR - +5VDC
- RD VI GN - COM
- BU - -12VDC
- VI - +12VDC
- WH - -5VDC
- dk gn - case gnd and bottom foil shield
