Working on an Otis LRV4 ..2-stop Hydro..about 1986 vintage. We replaced the relay board, and the mcb carstation board. The elevator still wont do anything. I have the 9v, and the 30v on the carstation board. (MCB).I have two LED on board lit..but buttons, P.I. doors will not lite or move, checked all fuses. DR relay is only function that moves when power is applied. Any ideas?

so where is the car..below the floor..the fact that only one relay is up the (DR)only means that you have doorlocks and gate circuit good..every other relay is a 24vdc which is activated by the ground signal output from the processor,to verify if you have a problem with the processor new or not easy test if all fuses are all good safety circuit is intact...ground the pm and umv or dmv inputs at the relay shelf terminal.if car runs up or down problem is processor...

I have two LED on board lit.

Which two?
Do you have your inputs?

You might have the I/O sheet in the back of the prints that will tell you your inputs and outputs.
Stupid question,but you did replace the chip(s) from the old to the new board didn't you?

This vintage car station board doesn't have all the little LEDs by each output or input. it only has three LEDs which is probably for voltage recognition . Think they were labeled 1,2,& 3. ( 1 &2 are lit)
I can move the car by jumping in PM starter & valve,but car will not do anything on its own. No matter where I put it in hoist way.
New board doest come with the two processor chips (U41 & U42) yes those have Ben swapped to new Board.

If all the dip switches are exact to original..I wouldn,t rule out the possibility of a bad replacement board, i,ve replaced 3 boards before I was able to get the car to run...you may even have a loose
wire connection or wire fell of the TB1-TB3 connect behind the cop,direction circuit intact..broken traveler..all places to check..

Yes bad boards are common,thats for sure.

But I wanted to add that those chips by all the inputs and outputs are "buffers" and replaceable.
Say,like you have you input coming to the board,but no output,replace that chip that corresponds to that IM or OM.

first thing i would do is to check every input in the cop terminal strips that feed the processor input wiring. does the car run on inspection? if not, first input would be the ES input which is a contact off of the stop switch. this controller has 2 stop switch circuits, one in the main safety circuit, and one that only feeds the es input. the other input would be DR. this is the door circuit, if Dr relay is picked which you indicated, then a contact on dr feeds the dr input , if it is not working, then the car will not run. hopefully you have the correct print, as there are some slight variations of the input circuitry on the lrv in regard to the MB terminal strips.

I have replaced the MCB board again. I have found if I plug in the om3, or om4 the bufers will heat up rapidly. Remember I have NO functions at all. I am not blowing any fuses, and all power supply are correct. The doors have no power. I have no lights when any buttons are pushed. No inspection movement. Nothing. I did find out that the building loss power to activate this. Lightning?.
I am on the track of bad software. We are looking for software now.

car should run on inspection even without software. pretty sure it will run even without a MCB. check your relay board inputs and outputs.

OM3 and OM4 are Nudge and up main valve outputs-they go through the traveler. Have you checked that your traveler is ok?

On any equipment, if you wind up frying the software and you have to buy from the OEM for replacement....Go ahead and spend the few bucks, and have the OEM do the replacement and check out of the equipment.

You'd be surprised how quickly your warranty can disappear, by the time the check is written and the chip hits your hand.

Check all plug connections on boards you swapped. Its possible you are off on one of the plugs by a pin.... Easy to do.

someone above mentioned the 24 volts. if I remember right, DR is an 120volt controlled relay and the rest are 24volt. similar problem a few years back were the 24 volts was lost on the relay board itself, resulting in the exact condition Greg describes and no fuses blew either. something to do with a regulator(?) at the 24 volt source on the relay board itself. I remember we were able to bypass it until a new board could be installed. pardon my vague recollections, but maybe it'll stir some thought and investigation.

Yes,that 24 volt regulator can go bad and easily replaceable.
Can buy one at Radio Shack,or use to.
They just plug in.
Forgot about that one.

guess we'll have to wait for Greg to get back to us with the fix. it's a drag when a problem is posted, then you never hear of the solution.

Fixing the relay board power supply is easy. As stated before you can buy the resistors and diodes locally-Some of those components on the some of the boards were rated barely big enough to withstand some of the current.

Thanks everyone, It turned out to be the 9vdc power supply at the top of car station. The meter would read that 9vdc was present. Witch is correct. Like I stated the two LEDs were lit also on the MCB board, assuming the power is fine. BUT, then we also found the power supply was putting out AC also...which was taking out our MCB board, and heating up the components very fast.
Another good one to remember. Thanks for all the suggestions.

Congrats on getting that one outta your hair!