Troubleshooting a MEP-005A

[Warthog]

I sold my MEP-005A 120/240 60Hz to a friend. It was working fine and now won't excite.

The engine starts and runs fine. I hold the start switch up to excite the windings. The Hetrz gauge swings to 60, and then drops to zero.

Any pointers on where to start looking. I have the manuals and will start reading.

I have never worked on the electronics before. Engines yes, electronics no.

Warthog

 

[Crash_AF]

After it drops to 0, have you tried re-engaging the switch to reflash the field? The starter shouldn't engage because the engine is running, but the field flash circuit should reflash the field.

Later,
Joe

 

[Warthog]

Just checked the unit. Upon startup the Hz gauge is zero (below 48 on the gauge). The Voltage gauge is zero. My volt meter shows zero on the convenence plug. The throttle is wide open. ~1800rpm

I hold up the start switch and the Hz swings to 62 then settles at 60. Voltage gauge show 75v. The convenence plug is showing 6-7v.

I release the start switch and the Hz swing to 62, then back to zero. The Voltage gauge drops to zero.

I even flipped the Battle Short and nothing changed.

 

[Crash_AF]

Battle Short just overrides the protective devices on the engine, it does nothing on the voltage side.

It's been 6 years since I touched a MEP-005, I'll check a couple of things and get back to you. This is a common enough problem with MEPs that haven't been used regularly... I'm just trying to kick the cobwebs off the memory banks... LOL I'm thinking you might need to manually flash the field, but I want to read over the TM again to make sure.

Later,
Joe

 

[Warthog]

I'm reading the TM 5-6115-465-34 manual now. Having never worked on these units before some of it is Greek to me, but I'll press on.

I'm thinking diry contacts some where.......

Thanks for your help.

 

[Speddmon]

I'll have to look into the manuals when I get some free time, but all of the MEP's I've seen are self excited...meaning once you get them flashed and producing power they self excite from that point forward. If Warthog was able to get it producing 60 Hz and about 75 volts, that should have been enough for the generator to take over from there.

But he did say his DMM was reading 6 volts at the convenience receptacle...so the qauges could be wrong. It might be later tonight, but I'll do some digging too and see if I can find anything.

 

[Warthog]

These are some pics I took a few months ago. Everything looked good.

It was working last week after we put in some fresh batteries. Then the next day this issue.

 

[Speddmon]

I glanced at the troubleshooting section of the TM 5-6115-465-34 just a bit ago. I didn't get to go in depth into it yet, but right on page 2-6 (Table 2-2 step 14) under the troubleshooting section it describes almost the exact problem you are having...

"Generator fails to build up rated voltage or voltage goes to "0" when START-RUN-STOP switch is released"

It tells you to test and repair the voltage regulator. I'm not sure about the larger MEP's but on the MEP-002 and 003's if the voltage regulator fails, typically the voltage goes high and you cannot adjust it back down. These larger sets could be different as they have a different regulator and control design.

I hope this helps some....if you are still having troubles let me know and I'll look into it some more.

 

[Speddmon]

Warthog,

Have you had a chance to look into this problem any more and come to a resolution? I'm curious

 

[Warthog]

An update to this old thread.

The guy I sold the unit to let it sit for a couple of years. We where expecting a snow storm and he wanted it running. He just couldn't figure out why any of the local generator repair shops wouldn't even touch it. Imagine that. A local shop not wanting to work on a 32 year old military unit. Hmmmmm

Being the nice guy that I am I pulled the static exciter control unit off, removed the cover and couldn't find anything out of place.

And then I started wiggling wires. Low and behold, the wires on the small buss bar (item #21) where really loose. Tightened every screw, nut and bolt and the unit works as it should.



Wait until he gets my bill.

So guys and gals, Clean and tighten those connections.

 

[bimota]

Off to try the same repair on mine with the same behavior - almost started shopping for a new voltage regulator assembly! I hope I get lucky!

Also need a speed switch for an MEP-006 - anyone got one in the bone yard - that I know I need.