MEP-003A odd problem with voltage and override

[Milhouse]

So the generator starts fine, as you hold the know in the override position waiting for the oil pressure to come up, voltage and frequency come up just fine, as soon as you release the override knob and it jumps to run position, the voltage is gone, no output at all from generator, engine still running fine but no output. Replaced the main board and voltage regulator, no change. Can't figure out what the override is doing to allow voltage to stay up only when on, any ideas?

 

[Chainbreaker]

When the Start knob is being held in the start position it also provides DC voltage to excite the generator. When you release it from the start position that voltage is removed as it should not be needed anymore once excited. Do a search of threads using various terms such as "MEP-003 MEP-002 generator excitation voltage" and you should get some threads discussing troubleshooting the issue and potential solutions. Also check the TM's.

 

[Chainbreaker]

Here's one thread that may help: https://www.steelsoldiers.com/showthread.php?182229-MEP-003A-Engine-Runs-But-No-Generator-Output


And yet another that covers more things to test: https://www.steelsoldiers.com/showt...-or-HZ-reading-on-meters&highlight=no+voltage

 

[Triple Jim]

The main components that supply the exciter field current are CVT1, which sends AC to diode bridge A4, and that diode bridge, along with all the associated wiring and switch contacts. That current is controlled by the regulator and a control winding in CVT1. It's not very likely the problem is with the regulator, but you can remove the wire from terminal 17, tape the end, and see if the generator output is then too high, like 170 volts where it should be 120. If so, the regulator is supplying too much current to the control windings.

CVT1 and board A4 are both in the box under the main output lugs.