MEP-005A Load Bank Test w/problems

[flydude92]

I recently had a high voltage problem with my MEP-005A and was able to fix it with
help from members of this site. It has been running great since then.
I’m only using between 5%-30% of the generators capacity do I decided to build a load bank
to test the generator and deal with any wet stacking problems that may exist.

The load bank uses a 55 gallon drum and eight 4500 watt 240 volt heating elements capable of 36K watts.

I ran it at 9k watts for a few minutes with no problems.

When I ran it at 18k watts (60%) the engine ran rough and surged as expected
but after about 30 minutes it began running smooth.

The trouble began when I added another 4.5K watts for a total of 22.5K. The best way I can
describe it is it ran for a second then voltage & amperage readings dropped to zero.
A second later it went back up and then dropped to zero a second later.
I let it run like this for a few minutes with no change. There were no error lights.

I added another 4.5k watts for a total of 27k. It continued to cycle on/off.

I added 4.5k watts for a total of 31.5k. It stopped cycling. It actually ran well with some
surging. I was unable to adjust the voltage. It was locked at 111v. I let it run for about 20 minutes.
The surging decreased but the voltage was still locked at 111v.

I couldn’t stop now so I added the remaining 4.5k watt heating element for a total of 36k watts.
I was surprised. It ran very smooth. Frequency was varying about .3 hertz. The voltage is
now 115V and still can’t be adjusted. I let it run for 15 minutes at this power setting and measured
145 amps.

I reduced power to 27K watts and the cycling resumed.

At 18k watts the cycling stopped, it ran extremely well and the voltage was able to be adjusted as usual.

Does anyone have any idea why it would cycle like that and only between about 18k-27k watts?
Also the voltage cannot be adjusted above 18K and locks at some voltage around 115v. It seem like the
regulator is working except for the ability to adjust the voltage.

I attached a video showing it cycling with 27k watts applied to it and one running with 36k watts.

Thanks,
Brian

View attachment Cycling at 27k.mpg

View attachment Running well at 36k.mpg

 

[Munchies]

Your running this after a single phase conversion?

Was it actually opening the contactor as it cycled?

 

[1800 Diesel]

Only things I can come up with is defective main contactor or loose connections somewhere...

Edit--on the voltage adjust issue, do you have a known-good VA rheostat you can swap out the existing with?

 

[flydude92]

Your running this after a single phase conversion?

Was it actually opening the contactor as it cycled?

I did sewerzuks single phase conversion when I bought the generator 13 months ago.
The contactor does not seem to be opening. The light never goes off and I can't hear it change state.

Brian

 

[flydude92]

Only things I can come up with is defective main contactor or loose connections somewhere...

Edit--on the voltage adjust issue, do you have a known-good VA rheostat you can swap out the existing with?

I have not checked the main contactor for loose connections but I will soon and let you know if I find anything.

I don't have a known good rheostat but my current one tests okay. I assumed it is ok since it works at lower power settings although I suppose it could fail under higher loads.

Thanks,

Brian

 

[1800 Diesel]

I did sewerzuks single phase conversion when I bought the generator 13 months ago.
The contactor does not seem to be opening. The light never goes off and I can't hear it change state.

Brian

While it's fluctuating, test & record voltages on the terminals on both sides of the main contactor. Sewerzuk taught me that one....obviously observe standard safety precautions working near high voltages....

 

[Munchies]

While it's fluctuating, test & record voltages on the terminal on both sides of the main contactor. Sewerzuk taught me that one....obviously observe standard safety precautions working near high voltages....

Yup, quickest way is to check the voltage on the generator side of the contactor and troubleshoot upstream from there.

 

[flydude92]

1800 Diesel – Munchies
Wow, I never thought of that.

Good basic trouble shooting techniques.
I wish I thought of that earlier.

I will check it in a couple days and report back.

Thanks guys,
Brian

 

[1800 Diesel]

1800 Diesel – Munchies
Wow, I never thought of that.

Good basic trouble shooting techniques.
I wish I thought of that earlier.

I will check it in a couple days and report back.

Thanks guys,
Brian

You're welcome! Good luck with it, be careful & report back. Standing by.

Kevin

 

[glassk]

realign the control unit in accordance
with paragraph 4-7j. Also follow this procedure
if the engine speed hunts.





TM 5-6115-465-34 4-22
that is 1770 RPM to 1860 RPM

58 hz to 62 hz

in the video seems like it is to me,

 

[sewerzuk]

I did download both of the videos you shot of your generator; your cycling problem is crazy!
I've never seen anything like that.
The fact that voltage cannot be adjusted tells me that the exciter/regulator circuit is the source of the problem, but I don't believe that I can point you toward a specific area to start troubleshooting.

I do, however, have a suggestion.
One member here on SS pointed out that I missed one lead movement; I haven't had another -004/-005 conversion to do so I haven't had the chance to re-test, edit, etc. my conversion process. However, I didn't feel any urgency in doing it, since the conversion has worked so well for so many people.
I don't know how thoroughly anybody has tested their sets after doing the conversion...perhaps your method of loading the set uncovered a problem with my conversion process on the -005's? I don't know...
The issue is this:
My lead movements changed the voltage being supplied to a control transformer inside of A11 from 240v to 120v. That control transformer supplies field current. It seems to work fine on the -004a, but maybe with the higher field current in the -005a it can't "keep up?" To correct this, you would need to move the X8HH16B lead from T8 to T7 (instead of from T8 to T11, as my conversion process currently shows).
I can't guarantee this will work, or fix your problem....but I have a feeling that it might.

 

[flydude92]

Sewerzuk,

It seems I can’t have the simple problems but it does make life interesting.
I did read the thread that flyanbrian started regarding his transformer coming apart. His suggestion to change the input
to T2 from 120V to 208V sounded like a good idea so last week I made the change to see what would happen. It didn’t
fix my problem but it did change the symptoms slightly as noted below.

120V to T2 primary:
When I went from 18K to 22.5K watts sometimes the generator began cycling other times it didn’t.
When I increased to 27K it kept cycling. At 31.5K it stopped cycling and voltage adjust was unresponsive.
When I decreased wattage from 31.5K to 27K the cycling resumed. When I reduced it to 18K it always stopped cycling
and the generator would return to normal.

208V to T2 primary:
When I went from 18K to 22.5K the generator always began cycling.
When I increased to 27K it kept cycling. At 31.5K it stopped cycling and voltage adjust was unresponsive.
When I decreased wattage from 31.5K to 27K the cycling resumed. When reduced to 18K it would continue cycling.
I had to reduce the wattage to 9K before the generator resumed working correctly. At that point I could raise it to
18K without a problem.

This morning I checked the DC voltage at F1-F2 while the generator was cycling. I had readings between -3v to +11v
and amperage was .5 to 10+. William at Delk’s suggested I disconnect F1-F2 from the regulator and supply my own DC
voltage to F1-F2. I wasn’t sure what amperage it would pull so I used a two amp variable DC power supply
and blew the regulator in the DC power supply. Since I don’t usually learn on the first try I used a second
DC power supply with the same results.
I then used a 250V AC variac and wired a 20 amp bridge rectifier to it (I wasn’t taking any chances on amps this time)
and the generator worked perfectly. I ran it thru 31.5K for 30 minutes with absolutely no problems adjusting the variac
as needed to maintain 120V.
Sounds like you are correct regarding my exciter/regulator being the problem.
The exciter/regulator does pass the bench test in the TM’s.

When I had the overvoltage problem I replaced most of the components on the regulator board. I still have a voltage
regulator IC and a couple multi pin IC that I never replaced. I suppose I can try replacing them and see what happens.
I don’t know if transformer T2 could be causing my problems and have no way to test it.

Brian

 

[flydude92]

Update: (finally)

It has been a long time since I last posted about this problem but progress has been made.

I recently purchased a scrap mep-004AAS that had a seized engine, is missing some outer panels and other
miscellaneous stuff. I purchased it to use as diagnostic/replacement parts for my 005. First thing I did was
clean, tighten and bench test the regulator assembly. I installed it on the 005 and my problem went away.
I was able to run the generator at 36K watts with no problems.

I replaced everything in the original regulator assembly except for the transformers and a couple power
resistors and it still would not work. Using the good regulator I verified the regulator card works and the
problem is in the regulator base.

I haven’t determined which part is causing the problem yet but at least I know it is in the regulator assembly
as others on this site had suggested. I plan to get it working so I have a spare.

Brian

 

[Keith_J]

Sounds like a transistor going wonky. These devices are switches, either on or off. It sounds like a transistor that has a frequency range where it is dead, not generator frequency but field switching freq.

diagnosing the the issue would require a o-scope output of the transistors during the load testing. Would be easier to just swap out all transistors.

 

[flydude92]

Actually I have replaced every component on the regulator board and verified it works by installing it on the replacement regulator assembly. Everything on the
regulator base has been replaced except for the 3 transformers and the two 55 watt resistors and they all ohm correctly. They may be failing at higher power settings.

Brian

 

[flydude92]

Final Update:

All I have to do at this point is figure out which transformer or power resistor is causing my problem.
I have always suspected T2 since it is the biggest transformer and it is looking very dark. I replaced
it with an NOS transformer. DIDN’T fix it.



Since I am really tired of screwing with this thing I decided to swap out the remaining transformers
T1 & T3 and the two power resistors R1 & R2. DIDN’T Fix it.

Crap

That leaves a wiring problem. I started at P11. The connector that goes to the regulator board.
Found the problem in 2 minutes. The ‘H’ and ‘I’ wires were swapped. I put them back were they
belonged and the generator is working perfectly to 36K watts.

It’s kind of depressing. Now that it is fixed I don’t know what to do with myself.

I just remembered! I have kids!

THE END

 

[Keith_J]

Wow, awesome fix. And that you had time to fix it WITH KIDS in the picture? I bought a MEP 026 about five months ago, all I have been able to do is fix the carb and get it running. Needs a complete fuel system, exhaust overhaul and load test. Have I done any of it? No, the answer is kids. Well, the patio construction, replacing doors, windows and exterior on the house...

 

[flydude92]

I put as much time in it as I could although money was also a deterrent. I couldn’t do
much until I got another exciter/regulator and I wasn’t about to spend $500+ for one.

It cost a whole lot less to rebuild the regulator I have.

Now with the scrap 004 I purchased I have a lot of spares parts.

Brian