I have a group of 4 1960s era otis with a small microprocessor overlay for fire service and dispatching and such. This is apparently the upgrade from the relay overlay. I have partial prints for the original, the relay logic mod and now a microprocessor mod. Im loosing my DO before the car gets into the floor so the doors do not open. I will try to post a pic if I can.

Make sure door reversal device is not firing cancelling door time. Some of the older stuff did not wait till door was open to cancel door time.

The DO ouput fires when in slowdown but drops before reaching the floor. The DO ouput pulls in the relay D1R and D2R aling with feeding the DZ brushes on the selector. Everything seems right until final slowdown then i loose my ouputs from the overlay

Traced the problem to a relay on the overlay circuit board not making. Replaced the board and it worked