MEP 003 VR repair.

[Triple Jim]

The rotating diodes get their input from the exciter rotor. The exciter rotor generates its power from rotating in the exciter field. On startup, the exciter field is energized by the flashing circuit. This means that it would be logical to verify that the flashing circuit is working before moving on to the rotating diodes.

 

[metalworker393]

Just checked A4 T6 and I'm only getting 1.3 volts, cleaned the ground too.

 

[Munchies]

I think we are getting warmer... I wont have access to the TM pdf's till tonight but follow the circuit. I know the main start swtich is in there, and those take a dump sometimes.

Actually I had one on this laptop.

This section overall is for you
2-10 or in your pdf reader hit Ctrl+f and search for "flashing"
When i get back home I will actually follow the circuit and help you find items that need checking

ENGINE RUNS NORMALLY BUT GENERATOR HAS NO OUTPUT.
1. Check voltage regulator (paragraph 6-6).
Repair or replace regulator.
2. Check exciter field (stator) for open or shorted windings (paragraph 8-2).
Replace stator if necessary.
3. Check diodes on exciter rotor (paragraph 8-2).
Replace diodes if necessary.
4. Check generator field (rotor) for open or shorted windings
Replace rotor if necessary.
5. Check generator rotor flashing circuit (paragraph 6-9).
Replace diode CR2 or bridge rectifier.
(paragraph 8-2).
6. Check generator stator for open, shorted, or grounded windings (paragraph 8-2).
Replace stator if necessary.
7. Check exciter rotor for open, shorted, or grounded windings (paragraph 8-2).
Replace exciter rotor if necessary.
8. Check bridge assembly A4 for defective resistor or diodes (paragraph 6-9).
Replace defective resister or diodes

 

[Triple Jim]

If you're getting only 1.3V at that terminal during cranking, then you need to look at the schematic on p. 1-9 of TM5-6115-585-34, and figure out what's not passing 24V to that terminal. If you can crank the engine, it's getting to TB4-3. Then it has to go through a couple connectors, so maybe you have some dirty pins there.

 

[metalworker393]

Hello and how are you. I just did the test where you hook a 12 volt battery to the terminals of TB3 -5 & 6. With a battery connected I was reading 37 volts on L0- L1 & L0 -L3 and 75 volts L1-L3 . Then my DC vr took a dive. Changed that out with one from a dead 002 I have and the charging circuit is working again. Thanks metalworker393

 

[Triple Jim]

Connecting battery + to terminal 4 and battery - to terminal 5 would send current through the exciter field, but I think I would apply it directly at the field side of unplugged J12 through a resistor if I were doing the test. Connecting a battery to terminals 5 and 6 would not give desirable results.

 

[metalworker393]

Hello and how are you. I was reading through TM5-6115-585-24p and on pg 151 (8-2) it details the 12 volt test. Tried it posted my results. I am next thinking of changing the wire harness as I have a 112 I bought as a parts machine. The harness carries the same NSN# so I would imagine they are the same. After that if I don't get any better results I am considering pulling the gen head and opening it up to look inside for any obvious damage. I don't have the tool but the electricians at work will "megger" a motor and they say either Good or shorted. When I was on my ship we had a rewind shop below the main machine shop. Didn't go down there unless I need to borrow their dial bore gauge or they wanted me to mic something. (would have been useful now right) I would like to get this unit making power again and if someone else is having the same trouble as me they can follow through. I don't have the tool to megger a motor and not planning on buying one. I have enough tools laying in the shed like a ship in the mothball fleet. Jim and munchies thanks for your time, patients, and help. ttyl metalworker393

 

[Triple Jim]

Yes, I see what I did wrong. P. 8-1 of TM5-6115-584-34 says to do what you did. I was looking at the terminal numbers on diode board A4, not TB3 when I said to use terminal 4 and 5. I'm glad you followed the procedure correctly.

 

[Munchies]

I think its odd there is a problem with the flashing circuit AND that it is way under voltage with an excited field. Too much of a coincidence.....

 

[Triple Jim]

Definitely something to consider.

 

[metalworker393]

Yeah it's weird, the machine was making power then just stopped making juice. The engine was just running along and no more power? It did start hard but the main breaker was off. After about 4 or 5 minutes of running the engine flattened out and was running good.

 

[Munchies]

I am going to say for right now rotating diodes.... I would dig deeper into that, with the proper tests and if they look iffy replace them. Try again with the direct 12v battery test and see where your at before you yank it for a winding test.

 

[Jimc]

not saying it is the diodes but if they are as bad and corroded as you say then even if its not them it wont hurt to change em out and clean up all the heat sinks. that would be one thing to cross off the list when done. those things are cheap and it doesnt take too long to do.

 

[metalworker393]

Hello and how is everyone today in this beautiful weather. So it looks like the 003 I've been working on is going to sit for a while before I change out the rotating diodes. I do have another 003 to tinker with. This is the machine that got the engine and fuel tank from the 112. Its running rite at 60 Hz and I checked it with my digital multi meter. Now here is the bad, The voltage on this machine is a little off (under) With the rheostat all the way to the left here are my readings- L0 - L1= 91.7 L0 - L3= 91.7 L1 - L3= 184.5 And with the rheostat all the way to the right L0 -L1=115 L0 - L3=115 and L1-L3= 230 My vr is No 72-5020 Do I adjust the R17 or the R15 to bring the voltage up? Thanks metalworker393

 

[Triple Jim]

It everything is working the way it should, R17 should be able to raise the output voltage to get the panel adjustment in range. Center the front panel knob and adjust R17 until the voltage is where you like it. Be careful, since there is plenty of 120V floating around in the control cabinet.

 

[Munchies]

If you cant get r17 to bring the voltage into rougly the middle of the sweep of the voltage rheostat/adjuster, then your VR is suspect. I have had them fail low on voltage, and have had voltage climb with load.

 

[metalworker393]

Okay, I'll try it tomorrow. If I turn it clockwise it should bring the voltage up correct? (R17) I did get almost a 25 volt change on each leg by turning the rheostat just couldn't get it up to 228-252 in the 120/240 configuration. I'll keep you posted. Thanks again, metalworker393

 

[Triple Jim]

You'll know very quickly if the direction you turn it is the direction you want.

 

[metalworker393]

Hello and how is every one in this wonderful summer warmth. Okay, machine #2- I turned r17 clockwise about 1 1/2 turns no adjustment. It bottmed out whatever is inside. Then stated turning it CCW and was able to get my voltage set (yay!) Okay now that every thing seems to be working back to machine #1. This is the one where I am not getting voltage. I looked inside the output box again with a flashlight looking for something obvious. I happened to see a crack in an item in the very bottom in the corner. I believe it is called the linear reactor. What does that do? I did't see any info on it other than a part # and a name. Thanks metalworker393

 

[Munchies]

Something I know nothing about. Never had to touch one! Eating dinner now but will look at a diagram to see what it does later. In the meantime from the TM

(5) Linear Reactor (Ll).
Disconnect electrical
connectors from control box. Use an ohmmeter to check
resistance of each of the three windings in the reactor
by checking resistance between terminals 1 and 2, 3 and
4, 5 and 6. Resistance for each winding must be 13.5 ohms
plus or minus 1.35, if not replace reactor.