MEP-002A quit generating under full load. Where to start

[rustystud]

My MEP-002A took a dump on me last week also. Our power went out so of course I started up the MEP -002a. I had to go to the store so I left my wife (who was sleeping) and my son to watch the house. When I got back the generator was still running but my son came out and said the power was off (Turns out he had everything on and then decided to "Microwave" his lunch) . So off I went to the generator building to see what happened. The circuit breaker had flipped but after I switched it back on the voltage went to max. I couldn't adjust it. So I wrote an "emergency" email to "Triple Jim" to buy his voltage regulator. I had to use the MEP-003A for the rest of the day and night. I hate wasting fuel but it couldn't be avoided . Normally the MEP-002A will easily run the whole house, but lately we have had such sucky weather we have had to have the A/C on and fans in every room running. It is raining but now the humidity is at 100% !!! I feel for you guys in the South-East states ! I couldn't handle it !

 

[Triple Jim]

As far as the different pots, it's just an update they made that was probably due to parts availability. They're electrically the same. You'll find the schematics to both boards in TM5-6115-584-34.pdf, pages 6-13 and 6-14.

Rustystud, it's on the way to you.

 

[CrzyDave]

Switched out the regulator board to one of unknown condition, and now I have 165VAC. I guess that means the spare board is also bad. These things must go a lot because the one that is making no voltage was not the original to my genset. It has a manufacture date of 1996 and my genset it 1989. It looks much newer and modern than the 1987 board I was testing with. So I am now ordering TripleJim's VR.

I wonder if they made the 1996 board in such a way that it would fail to no voltage vs. the normal high voltage failure. It would make sense, because it is more of a fail safe design. I'm really glad it didn't fail to high voltage when it was hooked up to my house! That might have bad consequences for TV's, computers, heat pump hot water heater....

 

[Triple Jim]

As far as I've seen, all the variations of the board are essentially the same circuit. They just changed a few small things like using one resistor instead of two in parallel in a couple places, and things like that. The ones I make are based on the 72-5338 design.

 

[CrzyDave]

Got my new ac regulator today. I don't think that was the problem though because I still have 0 volts. Odd because I have one really old regulator that puts out 165 vac, then mine and the new one put out .8vac. If I hold the start switch in start it makes proper voltage. I'm trying to switch out T2 right now because I have 150 ohms on left side and much higher resistance on the other spare here (which may or may not be any good) Anyone know what A1 does? It looks like a breaker, but schematic shows diode between a1-7 and a1-8. I don't see the other terminals on the schematic. I'm pretty lost at this point.

 

[CrzyDave]

Oh and I'm not sad about buying the nice VR!! What would make 0 volts on a good regulator and 165 volts with a bad or no regulator???? Seems like maybe CVT1 since when that's out of circuit, it makes the 165volts (removing wire 17 or installing burnt regulator).

How do I even start to test that beast?

 

[Triple Jim]

Disconnect the wires from either C1 or C2 on CVT1 and measure the resistance between C1 and C2. It's supposed to be 9.6Ω ±0.96Ω. That's the control winding.

The other resistances in CVT1 are in TM5-6115-585-34.pdf, page 6-15, which is page 93 in my PDF viewer.

 

[CrzyDave]

Ok will do when I get home tonight. I didn't see any of the terminals labelled on there, but I will look again and have another look at he manual. Seems easy to just swap out that whole box on the side. I think I can borrow the whole unit. I asked about the VR, and they let me take the entire control box, which is why I have spare transformers and all. Unfortunately they only have one know good genset and it's sold. The spare ones may or may not be any good.

 

[Triple Jim]

As I remember, the terminal designations are molded into the black plastic, but it's been a while.

 

[CrzyDave]

It's not that, I have 10.1 ohms there. I had to go by wire number shown in the chart.

I will just have to probe everything I that circuit. Thanks for the help.

 

[Triple Jim]

In any case Dave, sorry I lead you down the wrong path. When you disconnected the regulator and power came back, it *almost* had to be the regulator's fault. If you don't need the new one, I'll be glad to take it back.

 

[CrzyDave]

I appreciate the offer. I appreciate the help. Hopefully it won't be anything big. I'll figure it out yet. The power company has our property on a temporary feed luckily. We have a very long lane and the underground power line shorted. Then of course the generator broke.

 

[CrzyDave]

Ok I think I found the problem. Upon testing coils in CVT1 I found no continuity between H5 and H6. ( terminals for wires x38a16 and x11d16). This seems like it would could cause these issues. It looks like a pain to change out!

This is where the mouse nest was sitting so I imagine their pee got in there. Does this make sense to you TripleJim or others?

Symptoms are- field collapse with old and new voltage regulator hooked up, 136vac with it disconnected. Also, when flashing field with the start switch, I have proper voltage until it is released.

Thanks guys.

 

[Triple Jim]

I can't tell you specifically why a failed H5-H6 winding causes your symptoms, but you can be sure that is a major problem. Any chance you can dig out the black plastic, find the wires that go to those terminals, and fix the break? If so, you can put some electrical grade RTV on after the repair to seal it.

 

[CrzyDave]

Wow I don't know. I guess I need to pull the whole thing anyway. Worth a try. Could be in the winding though, not just the internal wire to the terminal

 

[Triple Jim]

A lot of times the problem is right near the terminal, if it's caused by something like mouse pee corroding things. If those terminals are in the clear, you might be able to excavate with the transformer in place. I can envision the connection between the end of the copper winding and the terminal corroding apart, so if you can expose it, you might be able to scrape it clean and solder it. I'm just guessing though, since I've never tried it on this particular transformer.

 

[CrzyDave]

Ok. I just pulled the whole output box and am bringing it in in bench. I was going to pull the selector switch, ct1 and cvt1, to try this. Maybe I can do it in place, but it's tight. Either way, it will be easier on the bench.

 

[Triple Jim]

I find it works much better if you're kneeling in gravel, with poor light, and with mosquitoes biting and ticks crawling up your legs.

 

[CrzyDave]

Haha. I got it out and the windings are fried. The potted side of transformer is all burned up, swollen and cracked by the iris marked "C". I will see what a new one costs tomorrow. Might be easier to do the Flight Systems regulator if this cost much at all.

After all this I'm not a big fan of the current/ volt transducer for voltage regulation. It's just so over complicated for someone like me that just wants single phase 240vac (it's really the reconnect switch that makes it complicated). I could basically gut that box and use TB2 to connect the gen head windings in the 240 single phase configuration permanently.

It all depends on if new CVT-1's are available and how much they are. Seems that and the ac voltage regulator are the common fail points on these gensets. I hate to use another even older used part.

Thanks again for all the help.

Dave

 

[Triple Jim]

Someone on this board might have an extra one to sell. I picked up a spare this way when I noticed cracks in the plastic of the one I'm using now.