The Comparator is used as a zero-speed sensor, Tach loss detector, overspeed sensor, and field loss protection relay. The relay is energized in normal running, if an error signal occurs that exceeds the the trip point the relay is dropped. the trip signal is 40 millivolts. You can check and adjust this on the board using an ohm meter. Common and the + trip point should read 4vdc. Adjust the trip pot cw till you reach 4vdc, or slightly higher to eliminate nuisance trips. The most common causes for trips are, the accel/deccel board adjustment to abrupt, clipping a doorlock while running, the brake dragging and heating the brake drum, and the motor field not adjusted properly. Also can be caused by bad boards and loose connections. Good Luck.

Thanks john. Ultimately we convinced the building owners it would be more cost effective long term to do a mod. Hopefully the motion 4000 we suggested is at least half as reliable as this has been over the years. 54 years of service. We did end up checking door locks, motor brushes, tach & tach brushes, all controller connections, meter tested SCRs, brake clearance, gearbox, adjusted TR2 for less rollback, without any luck. If we had some spare boards to swap out we could have tried it. We did discover that the elevator could not pick 1500lb of its 3500lb capacity without constantly tripping the comparator board which i think indicates motor and or drive components could be getting weak or out of adjustment.

update. 2EA board was bad. also we adjusted the leveling pot to give more juice during releveling. it would not relevel when a heavy load was placed on the car. it is running for now

Thanks for the update