I should add on this subject since the original question mentioned TAC 20. If you continue to get intermittent BP related selector faults despite checking magnets, replacing tape guides and boards, try hard wiring the Binary Position inputs back to the 188e. Its a well known problem that they are not reliable through LON. You need full IMS, a 5 pin red MTA, an 8 pin screw connector for the 188e and a couple of spare travel cable wires. Time well spent!
