Mep 803a no power

[Chainbreaker]

Regarding good components not working when installed on PCB. Have you taken a close look at all the solder joints of those through-hole components on the PCB? Vibration can play havoc on solder joints that were marginal to begin with. I recently had a card reader in my PC that was acting flakey after a couple of years. I removed it and using a loupe I was able to spot a bad solder connection on a connector that looked good to naked eye but was intermittent. I re-soldered it and no more problem!

 

[Triton]

Cjainbreaker, that's a good ideal, I checked them out today and everything seemed to be soldered really well. I'm checking the fets

 

[zarathustra]

Inside that regulator is a bridge rectifier on the quad input side, and a diode across the output terminals.. There are also two FET transistors (those are the large ones with the aluminum heat sinks).

The regulator that I fixed had that diode across the two output terminals shorted. In addition, one of the FET's was shorted. I replaced both FET's just to be sure.

The FET's are sorta hard to find; they have been discontinued and considered to be HAZMAT because they have a trace of some sort of material that is deemed bad -- probably a whole lot less than the mercury in a CFL.

If you cannot find the FET's, contact me; I have a few spares around the shop. I also have spare diodes that go across the output terminals.

The FET that was shorted in my regulator read 0 ohms between the two outside terminals. 0 ohms measured in either direction.

Removing a component from the board is a little tricky because it is double soldered - once on each side of the board. I used a small soldering iron and some of that copper braid that is made specifically for wicking solder off of a board. You will have to unsolder both sides of the board and even then it'll require a little wiggling to get the part off.

Use as little heat as possible, consistent with getting the solder removed, and with re-soldering the new part. Be wary of that little insulator between the heat sink and the transistor.

It is very easy to install a part wrong. Remember that all solid state components are VERY sensitive to polarity across their terminals and do not tolerate improper polar installation.

 

[Triton]

Zarathustra, thanks for the info, I have a guy that has a lot more knowledge about electronics than I do checking out the regulator. I pasted your info and forwarded it on to him so maybe that will help. I may have to take you up on the fet offer, I'll have to see how it checks out.
I noticed that the prices for a new one are all over the place, I saw one that sold on fleabay for $130 and I got a qoute for one that was $1,450.

 

[Guyfang]

$1,450.00? Man I am ready to go steal one, and sell it to you!

 

[fastimes98]

New member here and I hate to hi-jack a thread, but not sure how to post in the forum yet. I have an MEP802a that I purchased on GL and picked up in Ft Riley Kansas about 6 months ago. It is a Tier 2 reset and had 35 hours on it. I replaced all the fluids and it fired up fine. Last weekend I was using the 110 outlet powering a circular saw and suddenly it lost power to the 110 outlets. It still has 220 volts powering my travel trailer. I pressed the reset button, but nothing happens. Any ideas where to find the problem would be greatly appreciated. Also, I replaced the leaking fuel filter (one with the petcock) and the new one also leaks, is this a common problem?

 

[zarathustra]

There is a small button on the right side of the GFI controller -- it looks like a rocker switch. You can see and access that button with the front panel open. You can only access that button from the inside of the control box with the panel down.

Sometimes it is hard to see 'cause there are wire bundles running around that area. Chances are you triggered the overload and that just needs "a press" to get it working again

 

[TNriverjet]

Yep, the convenience outlet on the front is only a 10 amp circuit. Your circular saw probably won't cut much before tripping that breaker.

 

[Daybreak]

Howdy,
The convenience receptacles are only 10 amps.
Open the front control panel, look to your left right inside the panel. That is the reset for the outlets.

 

[myridge]

Did you ever get the regulator repaired or replaced? Was that the problem? I just bought one at GL auction and it's doing a similar thing with only 35v at the receptacle.

 

[Guyfang]

What has 35 volts? The 110 outlets? Or the load terminals?

 

[Guyfang]

New member here and I hate to hi-jack a thread, but not sure how to post in the forum yet. I have an MEP802a that I purchased on GL and picked up in Ft Riley Kansas about 6 months ago. It is a Tier 2 reset and had 35 hours on it. I replaced all the fluids and it fired up fine. Last weekend I was using the 110 outlet powering a circular saw and suddenly it lost power to the 110 outlets. It still has 220 volts powering my travel trailer. I pressed the reset button, but nothing happens. Any ideas where to find the problem would be greatly appreciated. Also, I replaced the leaking fuel filter (one with the petcock) and the new one also leaks, is this a common problem?

Hey partner. So how about telling us what happened?

 

[zarathustra]

These units are made to generate a small voltage without the regulator. The output to the convenience outlet follows a different path than the output to the terminals in the lower left of the unit.

If you are getting a small 20 - 30 or so volts out of the convenience outlets then it could be that the regulator is not operating. A quick test of this would be to measure the voltage at the convenience out let when you are first starting the generator. Once the starter disconnect kicks in the unit applies a DC voltage to the excitation windings to get things going while you are still holding the START switch in the START position. At that point you should see around 110 or so volts at the convenience outlets. Once you release the START switch that DC excitation voltage goes away and the regulator kicks in to keep things operating.

If the generator will make 110 or so volts during that short time that you are holding the START switch in START, but quits when you release the START switch, then the regulator is not doing its job. If it never generates the 110 volts at all, then it is likely one of two things...

First, a broken or misplaced wire or loose connector between the output of the voltage regulator (the pin number escapes me at this time) ---

or

Second, a bad stator. Replacing the stator is not too difficult, but one has to remove Sooooooooo many screws, at least 7 or 8 that have rusted together or the threads have stripped inside the nut. I wouldn't start to do that task unless I had the "new" stator in hand, a place where I could get that bearing that goes on the rotor (just in case), a good torque wrench, and a way to lift the stator(s). Last time I did this I used an engine hoist. I've not tried to do it while the engine is still on a trailer, but I think that could be a risky thing to do, what with the weight shifting "back-ards and forwards" and side to side with the CG moving in unusual directions.

There is also a bridge rectifier in the rotor. I don't think they go bad often, but that's a possibility.

good luck

z

 

[AOR]

I found this thread with a Google search. I hope to hear an update from the original person in this thread. I am also hoping that someone may be able to help me figure out what is wrong with a Mep803a that I have. I have not done anything with this unit in over a year. I own a few other Mep803a units that work well and I am familiar with how they work and how far different things in my shop will move the onboard output gauge. My notes state that that when I turned only my shop lights on the output gauge went to 75% and when I turned on one of the AC units the unit stopped producing electricity. It acted like it was overloaded and tripped some sort of output protection device. We recently lost power for about 5 days and I used one of my good units and the shop lights do not really move the gauge and when I ran 2 big propane heat systems with the lights I think the load may have been about 25% Any ideas on where I should start looking? thanks!

 

[Guyfang]

John did you have your load hooked up? At the load terminals? Or the 120 volt outlet?

 

[Triton]

With my generator the voltage regulator was bad. I had to replace it.














































































































































































































































































































































































































The other problem I had was that the previous owner put the wires on the alternator in the wrong place which ended up powering the S=1 switch, this kept the unit from turning off because of a power back feed. I am convinced that this is what fried the volt
age regulator.

 

[DieselAddict]

Its funny what you mention the alternator being wired up wrong. I had one that was also wired up wrong and in my case the diodes in the alternator were blown. This one came directly from auction with a fresh reset in that condition.

 

[Chrkjones]

what if I am getting 120 vac from convenience outlet until start is released and vac then drops to 22 vac? What do I check then. The Voltage Reg had 2 Burned/Bad diodes and I replaced. B4 that, I was getting 0 vac. Thank you for your help.

 

[zarathustra]

These generators were designed to give "a small AC voltage" if the regulator is not working or disconnected. I've found the "small signal" to be around 20 -22 volts AC.
This is both good news and bad news..... good news, the generator will generate AC voltage, so likely your rotor and stator are good. Likely, that is..

bad news is that unless something is connected wrong, it sounds like the voltage regulator is still bad. Since you have changed the diodes on the input side of the regulator, it sounds like you have opened it up. See those two power transistors?? they are the rectangular black thing that are screwed on aluminum heat shields.

One or both is bad. If you elect to replace them don't forget there is a small piece of mica insulation that goes behind them (usually). The transistors can be hard to find since they have been 'obsoleted" by manufacturers. Supposedly they contain hazmat.

If you use an ohmmeter across the transistor leads, a short across them or near short indicates a bad transistor. Measure across the leads with the leads + and - one way, and reverse the leads and re-test. If the transistor is shorted then it will read near zero ohms in both directions.

If I remember correctly those transistors are soldered in on both sides of the board. You'll need some copper braid to absorb the solder in order to get them out. I bought mine at Radio Shack... it comes in a roll. Since Radio Shack is RIP then any electronics shop will have it or perhaps ebay.

Use the smallest wattage soldering iron that will sufficiently melt the solder to re-solder any new transistors

good luck

 

[zarathustra]

By the way.... the voltage regulator is not powered by the 24 volt system. It is powered by a tiny AC winding in the stator that is rectified to dc within the regulator. for all intents and purposes the batteries are not connected to the regulator.