MEP002A no output

[Craig A Tull]

Hello all from a newbe
I picked up a 5kw genset this week and after re-installing the missing filters it runs fine but has no output, I found P60 and P57 (field wires) disconnected from TB3 5 and 6 indicating someone before me was trouble shooting the problem.
When I ohm out the wires I get nothing between P60 and P57 I do however get 55 ohms between P57 and ground, I see on the well faded schematic that there are fuses (F1 and F2) on the field but can not find them, anyone have a clue to as where they are???
I may have an expensive dud on my hands....
Thanks
Craig

 

[Speddmon]

Those are not fuses, they are the field leads, F1 and F2


If you have no continuity between f1 and f2 you either have a broken wire, connector unplugged or bad, or an open field winding

 

[Isaac-1]

To add to the previous post, check the contacts on the cannon plug where it goes into the control box

 

[Craig A Tull]

I would like to trace out the field circuit, can anyone tell me which Cannon plug and what terminals on that plug? I am having trouble finding the schematic in the TMs
Thanks

 

[Craig A Tull]

OK I found it, now I just need to figure it out

 

[Craig A Tull]

J12A and J12B, will check first thing in the morning.

 

[Craig A Tull]

I pulled the end bell and found a broken wire, fixed that and now I am reading about 32 ohms on the field, I can hold the start switch in the "flash" position and get voltage, I assume and would not be surprised that the broken and shorted wire fried the regulator, this should not be a big problem to trouble shoot and fix as component level repair is what I do for a living, it does look like more effort than should be necessary is required to remove the regulator, what were they thinking?
Thanks to all for the tips
Craig

 

[skidunits4you]

you should get voltage with the switch in flash position

 

[Craig A Tull]

I do see above

 

[Triple Jim]

Don't assume the regulator is bad if you haven't tested it. The problem could be something as simple as another broken wire.

 

[Craig A Tull]

Well I would not suspect another wiring issue as when the field lead (appeared to short and burn in-two) went the gen was finished, kaput, the pass transistor on the regulator tests bad, I have two of the three transistors in stock but of course not the pass transistor, hopefully I can get one tomorrow, is there a procedure for testing the regulator, if so I have not had any luck finding it.
Thanks
Craig

 

[Triple Jim]

There is, on page 6-12 of manual TM5-6115-585-34, but it takes a couple meters, a variable transformer, and T1 and T2 from the control box.

 

[Craig A Tull]

Thanks Jim, looks simple enough.
Craig

 

[Triple Jim]

I built one and would be happy to test yours for you, but I imagine shipping back and forth just for the test would not be worth it to you.

 

[Craig A Tull]

OK after getting the regulator on the bench at work and doing some component testing I don't see any problem there, I understand how the field is exited with the start switch through CR-2 but I am having a little trouble getting my mind around what roll CVT-1 is playing in all this, ok I can see how the secondaries marked X1 X2 and X3 going through a three phase full wave rectifier would produce field power, what I can not understand is the regulator "output" terminals 14 and 17 connected to the primaries marked C1 and C2 are doing, the "output" of the rectifier is DC and DC will not produce any voltage in the secondaries of the three transformers, I assume they are part of a transformer that also has the coils marked H1 through H6 and the DC from the regulator is some sort of "bucking" current?, I believe the issue lies somewhere in the CVT-1 and A-4 rectifier area. if the field wire shorted to ground as I suspect maybe it fried CVT-1 or the A-4 rectifiers, although it looks like the whole mess is not referenced to ground anywhere so I can't see how any current would flow to ground. I am having to learn more than I wanted to........

 

[Triple Jim]

CVT1 has control windings. By passing DC through them, the iron in the transformer can be made to saturate so that the transformer produces less current to be rectified and sent to the exciter field. To test CVT1, the rectifier bridge, and the associated wiring, you can disconnect terminal 14 of the regulator so that it doesn't supply the control current to CVT1. Then in a brief test run, the generator should put out well over normal voltage.

 

[Craig A Tull]

Yep two shorted diodes on the A4 board and a trace burned off the back, fortunately the three windings all ohm out the same, about 3.8 ohms so I think CVT1 is OK, Jim you also confirmed my assumption on the "bucking" current.
So it looks like I am on the back stretch on getting this thing to gen.
I have allot of diodes but I think I will wait and replace all of them tomorrow at work as its getting close to dinner time.
Craig

 

[Craig A Tull]

We are Genen now!! reg. working fine only a couple minor issues, the freq. meter is not working and the battery charging system is not working
Thanks Jim for the help!
Craig

 

[storeman]

Congrats! Sounds like the battery charging problem may lead to the stator or DC voltage regulator (or both). Stator leads should read 0.6 ohms, as I recall, when unit is off and leads disconnected. Should produce about 40 volts AC to the DC VR when unit is running.
Jerry

 

[Speddmon]

DC Charging System Test...Stickies