MEP-804A Voltage issues.

[Crankcase440]

I had purchased a MEP-804A from an auction and got it running. First issue was under current, only showing 50 volts and 50 volts at the convenience receptacle. So I had purchased and swapped in a new voltage regulator and now I have overvoltage. The hertz is reading correct and the potentiometer seems to be working for the herzt and I can hear the pitch change of the engine ram. The voltage gage is pinned at 500 volts and nothing changes that. This unit doesn't have the fuse mod (I read about that in another thread) and I am not that familiar with genset units so any help would be appreciated.

 

[Mullaney]

I had purchased a MEP-804A from an auction and got it running. First issue was under current, only showing 50 volts and 50 volts at the convenience receptacle. So I had purchased and swapped in a new voltage regulator and now I have overvoltage. The hertz is reading correct and the potentiometer seems to be working for the herzt and I can hear the pitch change of the engine ram. The voltage gage is pinned at 500 volts and nothing changes that. This unit doesn't have the fuse mod (I read about that in another thread) and I am not that familiar with genset units so any help would be appreciated.

.
First thing to do is to download the TM for your genset.
Then a little reading should help...

All the TM's you need to work on the MEP-804A

This should be all the TM's you need to work on the MEP-804A generator set.

www.steelsoldiers.com

 

[kloppk]

Be aware the 804As were built with two different AC Voltage Regulation systems.
Parts cannot be mixed between the systems.
One was a "TRC" system and the other is a "LIBBY" system.
There are 4 parts of each system that are unique to TRC and LIBBY.
They are:
- A1 AC Voltage Regulator
- T1 Transformer
- Front Panel AC Adjust Potentiometer R1
- Resistor R16 on the back of the 50/60 Hz switch

 

[Crankcase440]

.
First thing to do is to download the TM for your genset.
Then a little reading should help...

All the TM's you need to work on the MEP-804A

This should be all the TM's you need to work on the MEP-804A generator set.

www.steelsoldiers.com

Thank you, I had gone through the manuals ( I even purchased the printed manuals for the unit) especially the troubleshooting sections. I still not sure if I am dealing with a voltage regulator issue or if it is a damaged winding in the generator head. My knowledge of generator heads is rather

Be aware the 804As were built with two different AC Voltage Regulation systems.
Parts cannot be mixed between the systems.
One was a "TRC" system and the other is a "LIBBY" system.
There are 4 parts of each system that are unique to TRC and LIBBY.
They are:
- A1 AC Voltage Regulator
- T1 Transformer
- Front Panel AC Adjust Potentiometer R1
- Resistor R16 on the back of the 50/60 Hz switch

Yes I read that on another thread. I purchased another LIBBY Voltage regulator same model number (which may also be defective). Does anyone know if the aftermarket voltage regulators from Green Mountain Generator is compatible with all units? I will double check the other components to make sure one isn't compatible.

 

[Guyfang]

Just because you took a Libby out of your set to try and fix it, doesn't mean its supposed to have a Libby. You need to check all the other components, to make sure they ALL match.

If green mountain is selling VR's, and they are original military VR's, and they match the 3 other components in the set, then yes, they will work.

Is S-12 in the 60 hertz position?

Compare the TM date, and if it has Changes, to the TM's in our TM forum. The latest TM's with changes are in the TM forum.

 

[Crankcase440]

Just because you took a Libby out of your set to try and fix it, doesn't mean its supposed to have a Libby. You need to check all the other components, to make sure they ALL match.

If green mountain is selling VR's, and they are original military VR's, and they match the 3 other components in the set, then yes, they will work.

Is S-12 in the 60 hertz position?

Compare the TM date, and if it has Changes, to the TM's in our TM forum. The latest TM's with changes are in the TM forum.

You are absolutely right, I will check the other components to see if they are Libby compatible as there is no telling what happened prior to me purchasing the unit so swapping like for like may not be the answer.
Yes S-12 is in the 60 hertz position.
Green Mountain Generator looks like they manufacture their own version of the voltage regulators, but it eliminates the transformer and only will output 60 hertz. So I did not want to take the chance with the aftermarket if I could get what I believed was original equipment for the unit. But I will definitely go check out the other components for compatibility.