MEP 002A issue with ac receptable J14

[daigle]

Hi everyone! New here and very impressed with the knowledge in this forum. It has to be one of the best forums I've surfed.
I picked up a MEP 002a last summer from a town auction. I just started messing with it this year. Not sure how long it sat. But it's got about 1460 hours, with a rebuild in 1990. Must have been rebuilt around 1000 hours as it has roughly 460 since.

I got the unit running without much trouble. A few gauges need to be replaced due to seal failures. When using my fluke to verify voltage outputs, I noticed that all my voltages are spot on across each leg. But when I checked out the ac receptacle j14, I was barely getting anything. I removed the access panel to find that the wires to the 15amp circuit breaker (cb3) were disconnected and electrical taped. Thinking this was my problem, I reconnected the two wires and re-tested. Still no difference. I verified proper function of CB3 and continuity between CB3 and J14. After no luck, I started to chase wiring to check for loose connections and the sort. I finally found a wire which had been cut and left disconnected. It looked liked it should have been tied to TB2 by the way it was routed with the rest of the local wiring.

Here's where things get a bit funky. Figure 6-6 AC output control Box wiring harness on pg 88 of the "intermediate and depot level maintenance manual" is what I'm using as a diagram. The wiring diagram over the control panel can also be looked at as well. Both diagrams state that cb3 and j14 are connected together by wire x12a12. Mine is like this. Now, the other connection to cb3 should be from wire x3b12, which ties it to S6-L3. The second connection to J14 should be from X6B12, which ties it to S6-6.

Now, what's puzzling me is what should be my X6B12 wire is labeled X12L12. It connects J14 to TB2-8. What should be my X3B12 is labeled X9L12. It was cut, and connects to nothing, but it looks like it should have been connected somewhere on TB2.
I'm wondering if I should connect it to the S9B circuit on TB2-2?

Not sure why my wiring is labeled differently than my schematic. Also a bit confused as to why my connections are not consistent with schematic. I understand that S6 will feed TB2, but even then the connections aren't consistent with schematic.

I was hoping to be able to reverse educate myself on the wiring schematic. The reconnection switch S6 has proven to be a nightmare to understand. What makes it even more difficult is that my schematic and actual connection positions are not matching up, which just throws another wrench in the spokes.

Any ideas on this little tricky problem? I don't want to ruin anything by connecting X9L12 to the wrong terminal.
thanks so much for any help provided. hopefully it wasn't too confusing.

 

[jamawieb]

I'm sorry but do not have a specific answer to your problem but the wire coding in the 002a and 003a are slightly different from my experience. So you could have a 003a distribution box that someone retrofitted to the 002a so check out the TM for the 003a and see if it gives you your answer.

 

[Guyfang]

You should look at both wire schematics to confirm this.

Also, very important, is that the wire schematic on the metal plates, have "problems". There are several versions of the data plates, and most have some kind of mistake on them. Trust only the schematics from the TM's, and only the very latest edition of the TM, with the very latest change inserted into it. The TM's up loaded here in SS are in fact the latest, so if you have schematics from someplace else, compare them to the Forums schematics.

Also know that there might also be a problem with 400 hertz parts in your set. If you have never seen this set run right, then you have no idea what someone else did to it.

I would make sure you are using the right schematic, for the right box, and then un hook all the wires. Hook them back up IAW the schematics. If you have the patience and nerves. When ever I worked on a mess like this, in the end, it's just best to start all over again.

I have to go to work, but will look at schematics when I get home.

 

[Guyfang]

OK, back home. I have spent two hours looking at the 002A and 003A and 112B, (400 hertz) wire schematics. I can find no wire X12L or X12L12.

Please use the wire schematic on page 1-9 of the -34 manual. it's probably the most up to date. You are using the page numbers from ADOBE. page 1-9 is in ADOBE, page 35.

As you can see from the schematic:

J14-pin 1 (wire X21A12) goes to CB3, pin 1, and then out of CB3, pin2 (wire X3B12) to S6-L3.
J14-pin 2 (wire X6B12) goes straight to S6-6, which is jumped to S6-LO.

Anything else is wrong.

So now I want you to look at the front page of the TM you are using. Does it have written on the cover, THIS COPY IS A REPRINT WHICH INCLUDES CURRENT PAGES FROM CHANGES 1-6,7,8. Dated July 1977? If not, you are not using a current schematic. I look at Figure 6-6, page 88, (ADOBE) and could not see where you read that J14 is connected with wire X12A12.

I have a feeling your AC output box is for a MEP-112B, 400 hertz gen set.

Please take a look at these things. What does the data plate on the gen set say? Date of manufacture? Model? NSN?

If your set is real old, the schematic on top of the control panel should be sailed out into the wild blue yonder. There are lots of mistakes on the old plates.

 

[daigle]

Here are some photos of the data plates and ac output box

 

[daigle]

Thank you so much for your time, I greatly appreciate it!. My TM is exactly what you stated, so I went to figure 1-9 to recheck.
Just to clarify, my wire schematic states that I should have wires x3b12 and x6b12 as well. But, in fact, my actual wires in circuit are labeled X9L12 instead of X3B12, and X12L12 instead of X6B12.

My "X3B12" is currently open. My "X6B12" is routed to terminal 8 on TB2. in looking through the wire diagram in figure 1-9, i realized that TB2 is actually not shown as a fixed location, like TB1 is for example. "TB2" is scattered all over the schematic between s6 and the rotating exciter.

Is it possible they rewired to a TB2 location just to simplify wiring harness. Looks like each leg of the TB2 connections are used as some type of jumper for a common connection.

I guess to really simplify things, if I could find where S6-L3 and S6-6 are located, I can just easily rewire my harness to attach to these points. I'm having difficulties reading S6.

Now my curiosity is killing me as to why my circuit is relabeled and wires relocated. Thanks again

 

[Guyfang]

Thank you so much for your time, I greatly appreciate it!. My TM is exactly what you stated, so I went to figure 1-9 to recheck.
Just to clarify, my wire schematic states that I should have wires x3b12 and x6b12 as well. But, in fact, my actual wires in circuit are labeled X9L12 instead of X3B12, and X12L12 instead of X6B12.
The X9L12 and X3B12 wires can not be found in the wire schematics. Or at least not by me. I have looked 4 times now. Maybe someone wanted to repair the set, and simply used some junk wires from something else? Perhaps you should take two new pieces of wire, and rip the old two pieces out so you can replace them. Hook them up like the schematics. The new wire would be, if I did it, a different color, so later you, or someone else can SEE it's been changed/modified.
My "X3B12" is currently open. My "X6B12" is routed to terminal 8 on TB2. in looking through the wire diagram in figure 1-9, i realized that TB2 is actually not shown as a fixed location, like TB1 is for example. "TB2" is scattered all over the schematic between s6 and the rotating exciter.

See the diagram below.

Is it possible they rewired to a TB2 location just to simplify wiring harness. Looks like each leg of the TB2 connections are used as some type of jumper for a common connection.
At this point, we will never know.
I guess to really simplify things, if I could find where S6-L3 and S6-6 are located, I can just easily rewire my harness to attach to these points. I'm having difficulties reading S6.

The terminals should be marked. Finding S6-L3 and S6-6 might be a PITA, but should be doable. Don't forget, there are two different types of S6. I will try and see if someone has a picture of them both.
Now my curiosity is killing me as to why my circuit is relabeled and wires relocated. Thanks again

This is what TB2 should look like.
View attachment TB2.docx

 

[daigle]

Thanks for all the help! I was looking over my S6 switch and some of the terminals are labeled, others aren't. I couldn't find S6-L3. I couldn't directly find S6-6, but with the pattern from the actual labeled terminals, I can make an educated guess.

 

[Guyfang]

Don't thank me! You did all the work.

I guess, at the end of the day, you could use S6-L1 or S6-L2 also. It just makes it easyer for someone to troubleshoot, later on when it's by the book.

take care, and let us know how you work it out.

 

[Guyfang]

In TM 5-6115-584-34, page 6-20.1 and 6-20.2, there is a drawing of both type switches, and where the pins are marked on it, if that helps.