had a bad load weighing circuit on cop2 board, i borrowed a board from a friend to get the car running while our board was out for repair. Here is the problem, the borrowed board works fine, load set up nice, car runs great, the problem was that the top 10 floors would not light the car calls, bottom 10 floors would light, the car would go to the floors, but would not light the call light. ok so I'm thinking no problem, when we get our board back the problem should be solved. so we get our board back, load weighing works fine, car works fine, however now only the top 2 floors will not light the car light, car accepts call and will go to floor, but no light. now I'm thinking bad connections? redo all ribbon cables, same outcome. just to be sure i installed first board, and again car runs fine, but no lights on the upper 10 floors, put my original board back in, and now only top 2 will not light. talked to an otis guy and he thinks it may be something to do with the U12 chip, believe it is an eprom or eeprom any ideas

so after doing some investigating, i see that U12 is the eeprom that stores various info from the cop2 learn functions, i.e. load weighing, security etc. one of the modes is mode 1 which does a current check of all the outputs, and stores it in the ram so that if the current of a single output exceeds this learned current, the output is shut off so as not to damage the board. at least that is what i am concluding from what i have been reading. so here is my theory, I'm thinking that maybe the repair shop replaced the eeprom, as this could have been the problem with the original load weighing problem. and possibly since we did not do a mode 1 current calibration, that a couple of the memory locations have info in them that is prohibiting the output to come on. so i think i will go back and do a current calibration, mode 1 and see if this does the trick. what do you think

Just for laughs check the top 2 PB Lamps. I have a hard time getting my head around the Current calibration. The measurable Current from 2 lamps has to be in the realm of milli amps,plus all the induced voltage in the Travel cables over 10 floors makes this a head scratcher . If your theory works let us know.

john, the cop2 board is in the cop, so no travel wires. i know it sounds strange, but there is a routine that stores the existing current draw for each of the outputs from the board and saves it to compare each time an output comes on. I may be barking up the wrong tree, was just thinking out loud, probably check it out at end of week ill keep you posted

well my theory was correct, did a current calibration learn, mode 1 on cop2 board.
the routine turned on all pushbutton lights, buzzer etc. 72 in all. after that put car in service and now all the floor car call pushbuttons are lighting. the strange thing is that on the board that you select the different learn modes, the cmon current monitor switch was set to off. when we initially tried to do the calibration it gave us a W3 error, which said current monitor is off. turned the dip switch to on and redid calibration and it worked fine. i say strange because the cmon dip switch was set to off, i would expect that if it was off, it would not check current in outputs. any way it working and we left the cmon dip switch in the on position.

Glad I am retired. Excellent work Gator.