Troubleshooting Compu-Dobby® I & II
From AVL weaver Doreen McLaughlin
"The best way to troubleshoot a Compu-Dobby II equipped AVL is the "half method." In this instance, the components of the AVL Compu-Dobby II system are the computer box, the computer solenoid dobby box, the dobby fingers, the cabling, and the treadles. Since only shaft 13 is refusing to cooperate, the focus of the investigation can narrow down to the computer box, the computer solenoid dobby box, dobby finger # 13, and the cables for shaft 13.
To begin, turn off all power to the Compu-Dobby system. Get out your manual, and go to the section on changing your manual dobby for a Compu-Dobby (even if your AVL came with a Compu-Dobby the manual still has this section). Read the portion about how to remove the old manual dobby head and insert the Compu-Dobby box to orient yourself to the components I'm going to be discussing next.
Go to the side of the loom with the dobby box. Note that the computer solenoid box's pillow blocks are held in place by two retainer plates on either side of the dobby box. In the middle of the retainer plate there is a set screw with a nut. With a Phillips head screwdriver, remove the two retainer plates. Pull the computer solenoid box towards you. If you have a helper, have the helper hold the computer solenoid box. Do not disconnect any cables from the computer solenoid box.
Visually and physically inspect both the back end of the computer solenoid box (solenoid 13 in particular) and dobby fingers (# 13 in particular). There should be a minimum of dust and dirt. The dobby finger should move freely. Now check the cables running from the dobby arm up through and out of the dobby box. Does cable 13 have it's silver ball? Is it's silver ball the same size as the rest? Check the dobby arm. Is the slot where cable 13 goes in straight and narrow? If the answer to any of these questions is no, then you have cabling, or the slot portion of your dobby arm, to replace. Now, check the internal dobby head pulley. It is the pulley located in the top right-hand corner inside the dobby box.
Next, turn the solenoid box so you can see the solenoids. Turn on the Compu-Dobby. Watch all of the solenoids fire (move out and back in) in sequence. Did solenoid #13 behave as the rest or did it refuse to move? If it did not fire, then that solenoid has frozen up and needs to be cleaned/replaced.
If everything so far looks good, then replace the computer solenoid box into the dobby head (spring first, pillow block on the solenoid box next, then the retainer plate). Tighten the screws down on the retainer plate. Make a straight draw test draft with your computer and send it to the Compu-Dobby. With your helper treadling and you analyzing the action of the Compu-Dobby, watch and listen as shaft 1 raises, then lowers, shaft 2 raises, then lowers, etc., paying particular attention to shaft 13. Did the solenoid fire? Did the finger move? Did the cable get pushed into the slot on the dobby arm? Did the dobby arm "catch and hold" the cable (the silver ball should be at the bottom of the slot in the dobby arm)? Did the dobby arm then successfully pull down on the cable? Did the cables to shaft 13 move? Did shaft 13 raise? If so, then problem solved. If not, now you have a great deal of info to pass along to AVL."