If on any Dual changer, the run out adjustment on the segment (for 1219- segment’s eccentric pin for shut off rail) is insufficient to activate cycling, then the first thing to check is if the aluminium arm has a (sideways) bent which is hard to see because it usually occurs right at the juncture to the black bearing traverse in the tone arm support (gimble in your case). This happens more frequently as the alu tube gets thinner with the progressive model years. Even a slight bent can be enough to upset the arm positioning with bending in both vertical and/or horizontal planes. Since this bend also would shift the Start indexing, a client might have adjusted the start set down point, masking the arm problem.
The next issue is that (again any Dual) segment might be off rotationally which will exhibit the same phenomena as with the bend arm. A cure might be to loosen and rotate the segment slightly in favour of the missing distance of trip link (1219 item 158)
Next, is a problem with the cam's shut off levers and plate (1219- item 231 and 232) If they are too loose, the unit will cycle-repeat ad infinitum; if too tight, won't trigger in the run out groove. Follow the cam guide listed above in the Servicing Dual tt's above for the cure.
Lastly, the trip link (1219 item 158) was accidentally bent short. You can increase the rail's reach by slightly bending the contact nose outwards. Make sure the rail's (1219 item 158) contact nose stays parallel to the rest of the rail and that it is not bent too high and out of reach of the cams' shut off plate (1219 item 232).
Klaus Adlhoch, fmr. Assistant Service Manager,
Noresco -N.Q.I.-Dual of Canada,
Area of expertise: Tech Training and Consumer Service P.R.
Associated with Dual till Thompson era.
Favorite Duals: TG 12a, 1009, 721.