I really don't know what model you are dealing with but it had to be prior GMG given that you have 120 control voltage. Anyhow there are two relays on the amplifier board which drop EME. One really looks at a tach failure,or excessive error (difference between pattern and tach, Itl which is the boards are plugged in wrong. Given that you are not even trying to run yet, these are unlikely. The other really looks at excessive amplifier output or if the two shunt field SCRS are putting out near zero volts when the car is stopped or the armature voltage feedback is way out of range. One common problem is on all ELC/EVC units is one or two blown 20 amp fuses in the shunt field circuit. Basically the two SCRs form a half wave rectifier circuit to the generator shunt field. This is filtered by the six capacitors near the SCRs These are on the lower back of the controller on some units and inside the drawer on others. Another possible problem is a blown 6 pack, check the six capacitors near the SCR pack (back of controller) for holes blown in them. The EAO, Vel adjustments could be way out of wack (unlikely unless someone messed with them)or another sneaky problem that creeps up is a very noisy LRA relay. LRA is in the generator run circuit...but it is a 250 volt ac relay and makes a lot of noise as the lamination get old. This 60 cycle hum sneaks into the amp board and trips the EAO circuit. Another common failure on these older units was the wafer type switches they used for the RUN/SETUP and leveling select adjustments. Carbon dust builds up on these allowing Orange 120 vdc to back feed into the board logic creating all kinds of problems.
Last edited by Smitty; 10/27/12 12:36 AM.
