I am having an issue with door operation on a circa 1997 Montgomery Miprom hydro. The issue is sporadic door operation. In response to a hall call or car call the doors will do the following:

Open an inch and then close or
Open half way and then close or
Open fully and then close without any dwell time or
Sometimes operate normally for multiple runs

During any of the above mentioned operation, I never see DO7 nor DO10 ever get to 120VAC. The output led for either signal will be off, but I measure 10VAC or so (referenced to ground or L1A). When DO7 is inactive i do see the terminal as high as 55VAC. DO10 never reaches anything above 25VAC.

IF the door open, hall or car call button is held; the doors will open fully. During this failure all other inputs and outputs appear normal.

Others have changed the following in an attempt to resolve the issue:

Power supply card
All input cards
All output cards
Timer board
CPU
Input card back plane
Output card back plane
Relay board
Door operator motor
Mac 104 board (now an ECI replacement board)
Capacitor and transformer beneath operator board
SO cable from operator to Mac detector edge

I am kind of hung up on my output voltages being incorrect. My nudging output (DO4) also never changes state correctly voltage wise. All other inputs and outputs appear correct; input led on 120VAC, led off 10 or so VAC and output led on 10 or so VAC and output led off 120VAC.

Any ideas?