MEP-015a Low Voltage

Corvette1974

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Hello,

I have an MEP-015a generator that has always ran fine and puts out plenty of power. However, it has always put out slightly low voltage, even if the voltage adjusting knob is at full adjustment. The voltage is about 115.5 at no load. I went through the military TM and checked out each measurement and it seems everything checks out for the most part. The variable resistor is perfect, and the rest of the measurements were ok. The one measurement that is supposed to be 20V is only about 15.5 volt though, which is the same amount that the output voltage is low.
Any thoughts on how to check/repair this further? The voltage does adjust based on the variable
resistor being rotated (I can lower and raise it, just not enough).

Let me know what you think.

Thanks,

Will
 

Guyfang

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Hello,

I have an MEP-015a generator that has always ran fine and puts out plenty of power. However, ithas always put out slightly low voltage, even if the voltage adjusting knob isat full adjustment. The voltage is about115.5 at no load. I went through the military TM and checked out eachmeasurement and it seems everything checks out for the most part. The variable resistor is perfect, and the restof the measurements were ok. The onemeasurement that is supposed to be 20V is only about 15.5 volt though, which isthe same amount that the output voltage is low.
Any thoughts on how to check/repair this further? The voltage does adjust based on the variable
resistor being rotated (I can lower and raise it, just not enough).

Let me know what you think.

Thanks,

Will
What one measurement is that? Do you mean the measurement between terminals 5-6? If so, the TM tells you the volt regulator is bad. The volt regulator controls the exciter voltage, which controls output voltage.

(c) Using a multimeter, check the voltage across the output terminals to verify the reading on the set voltmeter. If the voltage is low and adjustment of the variable resistor will not correct the deficiency, check the exciter voltage across terminals 5 and 6 of the voltage regulator. This Voltage will vary but should be about 25 volts. Ifno voltage appears on the regular terminals, the voltage regulator is defective and should be replaced.

(d) If voltage across regulator terminals 5 and 6 is satisfactory, stop the generator set, attach the load cables, and restart the set.

(e) If voltage is still not satisfactory, replace the voltage regulator and repeat steps (a) thru (d) above.
 
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Corvette1974

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What one measurement is that? Do you mean the measurement between terminals 5-6? If so, the TM tells you the volt regulator is bad. The volt regulator controls the exciter voltage, which controls output voltage.

(c) Using a multimeter, check the voltage across the output terminals to verify the reading on the set voltmeter. If the voltage is low and adjustment of the variable resistor will not correct the deficiency, check the exciter voltage across terminals 5 and 6 of the voltage regulator. This Voltage will vary but should be about 25 volts. Ifno voltage appears on the regular terminals, the voltage regulator is defective and should be replaced.

(d) If voltage across regulator terminals 5 and 6 is satisfactory, stop the generator set, attach the load cables, and restart the set.

(e) If voltage is still not satisfactory, replace the voltage regulator and repeat steps (a) thru (d) above.
I will have to confirm if that was the exact one I am referring to. It may be though - I swear that the TM I saw and was following said "voltage should be 25v....but the voltage regulator is only bad if there is a reading of 0v." Meaning it doesn't mention any value slightly less than 25v. I will find out again. If it is the VR, any thoughts on replacing this?

-Will
 

Guyfang

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Will,

There were a kazillion 1.5 KW's made. So there has got to be some Junkers some place. Try putting an add in SS. Bump Supeman. Google the part number and NSN. I haven't had a 1.5 volt reg in the hand in 10 years, but I seem to remember that the back side, is compleatly filled up with potting compound. So no possibility to adjust it. But look, my moth eaten brain may not remember right. There's a schematic in the TM, I think, so maybe you can find someone to make one?
 

Corvette1974

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Will,

There were a kazillion 1.5 KW's made. So there has got to be some Junkers some place. Try putting an add in SS. Bump Supeman. Google the part number and NSN. I haven't had a 1.5 volt reg in the hand in 10 years, but I seem to remember that the back side, is compleatly filled up with potting compound. So no possibility to adjust it. But look, my moth eaten brain may not remember right. There's a schematic in the TM, I think, so maybe you can find someone to make one?
Haha! I will repeat the test and confirm that was the value I was talking about. Will keep you posted. Will check for available replacement.

-Will
 

Corvette1974

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Will,

There were a kazillion 1.5 KW's made. So there has got to be some Junkers some place. Try putting an add in SS. Bump Supeman. Google the part number and NSN. I haven't had a 1.5 volt reg in the hand in 10 years, but I seem to remember that the back side, is compleatly filled up with potting compound. So no possibility to adjust it. But look, my moth eaten brain may not remember right. There's a schematic in the TM, I think, so maybe you can find someone to make one?
Any thoughts on just ditching the 1960s electronics and installing an SX460 clone? That seems to be the go to method for both military equipment guys and other generator replacement. At $30 vs $130 it may be a good deal... Even though it is Chinese, electronics have come a long way.

-Will
 

Guyfang

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If it works, and you are only thinking about power, why not?? If having it look like it came from the factory is what you want, then of course no. What do you use it for? How is the reliability of the SX460?
 

Corvette1974

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If it works, and you are only thinking about power, why not?? If having it look like it came from the factory is what you want, then of course no. What do you use it for? How is the reliability of the SX460?
If it works, and you are only thinking about power, why not?? If having it look like it came from the factory is what you want, then of course no. What do you use it for? How is the reliability of the SX460?
I prefer factory, but when parts become ridiculously expensive and look worse than the one that I have it may be the right time to move on to newer things. I think it should have a very acceptable service life, considering people have used them in much much larger generators than 1.5kw. I checked the wiring diagram and it shouldn't be a problem to install it, and it even allows the use of the variable resistor to change voltage. For $30 it is worth the chance I think.

I only have this generator for a worst case scenario where I need power for lights/tools to repair my bigger MEP-003a if that were to go down. Otherwise, that powers the entire house no problem.

I'll keep you updated if I do end up doing the swap.
 

Corvette1974

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Alright so the problems start immediately... I got the sx460. It already will require modifications to fit into the control box. Does anyone have any insight on wiring this sucker? The wiring would be very simple, however it has the voltage transducer for the gauge. Does that have any effect on the wiring, or can I just wire it right in place of the old VR and be good?

Let me know what you think.

-Will
 

Guyfang

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Without seeing any documents from the new regulator, kinda hard to say. Or for me anyway. I have no experance with the SX-460. Having said that, the frequency transducer should not be a problem. It needs a voltage from your AC output, to convert to DC for the meter. I would assume the sx-460 also monitors the AC output. So there should be no problem.

If if you do a search for six-460, there are several threads that discuss how some others have hooked it up, and the posts are made by some smart people who know what they are talking about. It would be a good idea to take a look see.
 

Corvette1974

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Without seeing any documents from the new regulator, kinda hard to say. Or for me anyway. I have no experance with the SX-460. Having said that, the frequency transducer should not be a problem. It needs a voltage from your AC output, to convert to DC for the meter. I would assume the sx-460 also monitors the AC output. So there should be no problem.


If if you do a search for six-460, there are several threads that discuss how some others have hooked it up, and the posts are made by some smart people who know what they are talking about. It would be a good idea to take a look see.
Thanks for the input! My biggest worry was if the transducer and the SX-460 can coexist. I think you are right that it really shouldn't make any difference. The wiring diagram for the MEP-015 seems to indicate that the same 4 wires that went to the original VR can just be hooked up right to the new sx-460. The wiring diagram of the sx-460 seems to indicate that as well. What others have done for their generators (MEP-016, etc) are exactly the same.

Biggest issue is that I'm going to have to make a custom bracket to hold the SX-460 as it will not fit in the original location of the VR. It is too large. I think I have a good idea...when I get it done I will post up if I am successful.

-Will
 
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