Me 004a transformer went out, then had other troubles.

[dlocklear41]

My Gen Mep-004a had been running fine for years then one day a puff of smoke out the back. Found out the stator box was bad as the transformer had fried. After replacement of the box, I could not get the hertz and volts needle to rise on the restart after the repair. I got someone to try it on theirs and it worked fine. Put it back in mine but still no hertz nor volts. I'm new to this, can anyone give me suggestions on what might be wrong?

 

[R Racing]

Did you flash the field ?

 

[dlocklear41]

How?

 

[dlocklear41]

I was instructed to use a 9 volt battery on a f1 wire. The two meters jumped when I touched the f1 to the positive side and the other to the neg. Is that flashing the field?

 

[R Racing]

Nope there is a easier way . once the engine is running and you have set the throttle up to near proper speed. Turn the starter switch on again for about 3-5 seconds. The starter will not Engage !! it will only flash the field and you should see voltage and frequency.

 

[dlocklear41]

Yes I did that several times.

 

[DieselAddict]

Have you measured the output of the generator terminals or the convenience outlet to check voltage and frequency?

 

[dlocklear41]

Had someone do it and there was nothing.

 

[DieselAddict]

When you held the START switch did you see the needles jump at all?

 

[dlocklear41]

They vibrate but not jump. The ac voltage fluctuates minimum and the percentage guage fluctuates at about 20 % . Nothing other than that.

 

[DieselAddict]

Need to troubleshoot the rotating assembly on the exciter.

 

[1800 Diesel]

Yes I did that several times.

Did you happen to notice if the starter teeth "grinded" when you placed the start/run/stop switch in the start position while the engine was running?

 

[dlocklear41]

I didn't hear anything unusual. Even the other person didn't and he works a lot on various equipment. Someone mentioned diodes. Is this something that might go out with the transformer?

 

[DieselAddict]

Can you tell us more about what the generator was doing when the magic smoke came out? Was it idling or was it up to speed? Was it connected to a load and making current?

 

[dlocklear41]

I started as usual and noticed the two gauges did not come online. I reved the engine to approximate speed and tried to re-excite. Nothing. I went into the house swapped overrelays. Went back to generator and loaded the generator with load. The needles came up but dropped back out. I re-excite and again needles came up and then dropped. That is when I seen the puff of smoke out the back. I quickly shut it down.
I opened the right side and found the exciter box took it out. There I found the stut on the side. Opened it up and the transformer fried. Replaced the exciter box out at Delks. It did not work. Tried in another generator and it did. Back in mine as still will not move needles. After exciting and getting no results, I was told to use a nine volt battery and the gauges did work. Called back William at Delks and he said diodes. I pulled out materials but I don't have expertise to pull diodes from there. Wondering if something else I could check before tackling diodes?

 

[DieselAddict]

How long did it run at low rpm?

I do think you need to dig into the rotating rectifier.

 

[dlocklear41]

Maybe a minute while warming up. Forgive me for asking... where is the rotating rectifier?

 

[DieselAddict]

Its on the end of the rotor. Letting them idle is a killer for the voltage regulator circuits. You should fire them directly to operating RPM. No idling.

 

[Sephirothq]

are you talking about the diodes on the Voltage regulator board? They can get corroded and the potting material is difficult to remove. The best thing I have found is to use a heat gun to get it soft and scrap it off. then soldier in new diodes.

 

[dlocklear41]

Looking to order diodes. 1N1109, and 1n1109r. Do I order three of each and where is best. If I replace a set ml ight as well replace all.