MEP-831A Is not getting power to fault module

[2Pbfeet]

FWIW: There are modern, non-milspec versions of that TVS available, as they are used in lots of circuits to limit surges. E.g. this one from Vishay, but LittleFuse and others make versions as well, some cheaper, but keep an eye on the power rating as the original is/was 1,500W rated;
https://www.newark.com/vishay/1-5ke220ca-e3-54/tvs-diode-1-5kw-220v-1-5ke/dp/05R5947 $0.8 retail, plus shipping. 185V, 1,500W rated.

Merry Christmas all!

All the best, 2PbFeet

 

[Thumpin]

That is nice to know there are alternate choices to the original MIL spec units - when I looked online for the original units they were $107 each!!!!!

So that makes we wonder. Should I keep using the 20 year old original TVS units.....or just go ahead and replace them all with new ones? Which will provide more reliable/dependable servide?

Merry Christmas!!!!!!!

 

[2Pbfeet]

That is nice to know there are alternate choices to the original MIL spec units - when I looked online for the original units they were $107 each!!!!!

So that makes we wonder. Should I keep using the 20 year old original TVS units.....or just go ahead and replace them all with new ones? Which will provide more reliable/dependable servide?

Merry Christmas!!!!!!!

I think that is a personal call. If it were me, yes, I would replace them. In my experience, TVS tend to work until they don't, usually with a voltage surge beyond their limit. Their relatives, MOVs, wear with each event.

If you are interested, here is a technical paper on the failure modes of TVS;

https://www.vishay.com/docs/88440/failurem.pdf

All the best, 2PbFeet

 

[Thumpin]

I just wanted to provide an update.

I got back home from the holidays and have been working part time on the MEP831A.

The new parts for the electronic repairs arrived yesterday. I will work on getting them installed in the next few days.



I drained the foul smelling diesel out of the tank, and I have been working on repairing the fuel sender, cleaning out the crud in the bottom of the fuel tank and replacing old hoses.

I was able to get the fuel sender working again by taking it apart and cleaning off all the brown coating by using E85 in my ultrasonic cleaner....it now works properly.

I then went after the crud in the bottom of the tank - it had a combination of flaky debris and some really sticky goo that resembles thick, dark Molasses. I took some of the goo out and put it in a glass jar to see what would dissolve it. Gasoline, diesel fuel, mineral spirits, naptha and several other things I tried had no affect on it. The only 2 things I found that had any affect on it was Acetone and E85 fuel. When you put E85 in the glass jar with the goo nothing happens at first - then the next time you look 20 minutes later the goo is gone and the clear E85 is brown. I went and got 5 gallons of E85 and I would put a gallon in the tank and let it sit for a while and wiggle the generator around to slosh the E85 around, then open up the drain and get it out (I did not want to get the E85 high enough that is was covering the floats for the NO FUEL sensor float). Each time the E85 came out a bit less brown and I thought I was doing good. The flaky stuff is all gone - however I keep finding little spots of the brown molasses goo. This morning I put hald an old sock on a wire and put in a little Acetone in the tank....then wiggled the sock around and it kept picking up more of the brown molasses. I repeated this until I used up 6 old socks and the socks were coming out pretty clean. I did some internet searching on this and this goo may be parafin that has congealed from old diesel fuel. Since diesel fuel doesn't seem to dissolve it - most likely any remaining goo will just stay on the bottom of the tank. I may try some SeaFoam in diesel fuel in my little glass test jar and see if that mixed into the diesel will have any chance of cleaning out the remaining goo - I likely would hook up a fuel pump to the tank drain and run the diesel/SeaFoam mix through the tank for an extended peroid rather than running the mix through the engine. (I am afraid of putting too much E85 or Acetone in the tank as it could damage the fuel level sender or the device that monitors the "Empty" fuel sender/and axiluary fuel pump sender.



Today I am getting the new fuel lines and filter installed.

 

[Thumpin]

Well I did some more work this evening after dinner.

I made my first ever attempt at a "Trace Repair" on a circuit board.

I started with this:



And after watching a few YouTube videos on the repair methods, I was able to get a decent repair for my first try. The circuit tests out good with an ohm meter.



When I did the test on the Fault Module - it now shows the Low Oil Pressure circuit to be stuck "ON" - but everything else tests good. So evidently there was some other damage done - most likely the Thyristor associated with the Oil circuit. I will get a friend to help me replace that item - that is far above my skill level with the crappy soldering iron I have.

 

[2Pbfeet]

There's a trace in the lower right of your second photo that looks from afar as if it is showing signs of having been overheated, and perhaps cracked. Is it still ok, and are the components it is attached to ok?

All the best, 2PbFeet

 

[Thumpin]

2PbFeet: Thanks for the head up on that trace. I looked it over and it appears to be fine in person....the photo I posted makes it appear sketchy.

The Fault Module is "stuck" in a "Low Oil Pressure" condition. Now that the burned trace as been repaired...all other modes check fine. The Fault Module does energize the "Engine Shut Down" and sends 24 volts to Pin 5 as it is supposed to.

I decided to install the Fault Module into the generator and see what it does - as I wanted to see if the replacement of the bad TVS at relay K12 with a good one solved the issue of burning out the circuits in the Fault Module. The good news is that when the Fault Module was installed and switch S1 was turned ON...the Fault Module energized the engine Shut Down by activating relay K12....and both the stuck Low Oil Pressure and No Fuel lights came on (there is currently no fuel in the tank). Adding fuel will fix one of those - but the stuck Low Oil Pressure circuit is not that easy to resolve.

So it appears the initial problem that burned out the Fault Module is corrected - now I just need a good working Fault Module.

I have a friend who used to work at a place that repaired communication radios (Mobilcom), and he is going to come over and try replacing the Thyristor for the Low Oil Pressure circuit. Hopefully that will resolve that circuit being stuck "ON".

 

[kloppk]

Is LOP stuck ON even with the LOP switch disconnected?

 

[Guyfang]

This is the key. Because as far as I have read this post 3 times, you NEVER mentioned that the LOP has been changed, tested OR checked. You might have a bad or mis-wired LOP.

 

[Thumpin]

I checked the LOP circuit in the generator without the Fault Module connected....and the switch and wiring is fine. The switch on the engine is "closed" when the engine is not running, and the switch is "open" when the engine is running. The wiring doesn't have any shorts to ground, and it test with "0" resistance from the Fault Module connector pins.

With the Fault Module in the test fixture I made, the LOP light comes on as soon as the positive and negative wires are connected to the Fault Module (in the test rig). As I go through the test procedure in the fixture - all other lights come on when the jumper wire is connected as instructed, and all lights clear when the TEST/RESET switch is activated. Except.....the Low Oil Pressure light is always on and cannot be cancelled. (I realize my test fixture is ugly - but it works and didn't take long to make).

I have attached a photo of the test fixture with the original Fault Module hooked up. This module has the burned Thyristor...and I suspect that both the Low Oil Pressure and No Fuel circuits may both be bad....and maybe more! Neither the Low Oil Pressure or Low Fuel lights will come on when testing them alone - but on a few of the tests the NO FUEL light will come on while testing other circuits!

When I test the Fault Module I got from Kurt - now that the trace has been repaired everything checks out OK....except the LOP light comes on as soon as you hook up the electricity (even though the sensor wire is not connected to anything in the test fixture. The fact that the LOP light comes on without that circuit being tested......makes me believe the "switch" is stuck ON. It is likely the thyristor that is connected to that burned circuit....and tracing from the LOP pin in the connector to the burned trace goes right to the thyristor marked "Q2" on the circuit board.

 

[Thumpin]

A bit of time has elapsed since I was able to do any work on fixing the Fault Module - snow, single digit weather and a few other projects got in the way!

A friend who used to work repairing Motorola radios came over and replaced the Thyristor in the damaged Fault Module - the one that had the "Low Oil Pressure" warning light stuck "ON".

The repair was successful and the Fault Module tests good on the bench using the test procedure - and when installed on the MEP831A it functions just fine. The Low Oil light comes on when the power switch is turned on - but goes out as soon as the engine is started. The engine runs smoothly with the Kurt Klopp governor control doing just fine.

But unfortunately I have found another issue:

The inverter is working well when in the 120V mode - I can power an 1,800 watt heater off either side of the outlet properly. The problem comes when I switch to the 240 volt mode. Without anything plugged in I can CLOSE the power circuit and nothing is tripped - a voltmeter shows I have 120V between the Neutral and both L1 and L2, and 240V between L1 and L2......however whenever I plug the heater into the outlet the "OVER VOLTAGE" trips in the Fault Module and shuts the engine down. (This happens with both the repaired Fault Module - and an undamaged Fault Module I was able to buy off eBay...both modules test fine using the test procedure in the Technical Bulletin). Also the outlet is wired properly, and the adapter I am using works fine on my MEP802A and the wall outlet for my welder.....I don't believe anything is wrong with the outlet or adapter wiring.

NOTE: If I disconnect the Fault Module the Inverter appears to work just fine in the 240V mode. When I hook up the 1,800 Watt heater the voltage on each leg tests at 120V on each leg and 240V between L1 and L2 when I use a hand held meter. The volt meter on the generator reads 240V and the power usage meter corresponds to the power the heater requires. The only thing that appears weird is when I plugged a 120V fan into the other leg - the power usage meter on the panel showed the power usage dropping a few hundred watts....rather than going up a few hundred watts. I have not yet plugged any 240 volt appliance into the power outlet.

I suspect something in the Inverter is acting up and not happy with the operation in the 240 volt mode. I will try using a smaller energy load and see if that makes any difference, and I will look at the Technical Manual and see what tests/solutions they may list for this problem....and do a search on this forum to see if I can find this issue being discussed.

If anyone has an idea why the inverter can work well in the 120V mode but not in the 240 volt mode - please let me know.

 

[LuckeyD]

Good Day: Seems the fault modules are OK, and the K3 in the A8 is also working, but not right. The M2 is working but it gets its drive from the A8. Things are pointing to the A8. Recommend a hard job. Remove the A8, carefully checking all inputs and put it on a bench and look inside to see what may be overheated, bad traces, anything out of ordinary.

 

[Thumpin]

I have not yet taken anything apart - but I did a bit of experimenting to see what happens to trigger the shutdown and over voltage fault.

In the 120V mode there is no issue, and I can power 120V appliances without any problem. I can plug in a 1,500/1,800 watt heater, a 500 watt light and a big furnace fan and they run just fine.

When I switch to the 240V mode I can run all of the above listed appliances fine - as long as I keep the loads somewhat balanced on each leg. I can run the 1,800 watt heater on one leg, and the blower and light on the other leg. If I can keep the legs within 1,000 watts of each other the Fault is not activated and the generator keeps running. If I have the heater set on 1,500 watts and unplug the fan and only the 500 watt light is on the other leg - then the fault triggers and the generator shuts down.

This is a problem for me - as my intended use is to connect this MEP831A to my 240V generator hook up for my house if we get into an extended power outage. As the appliances in my house turn ON/OFF, there is no way to control the potential imbalance of the loads. It is not unusual for one leg of our house to require 2,000 watts if the fridge and freezers come on at the same time - while the other leg is only running some lights. (It is a bit convenient to have the fridge and freezers on the same 120V leg, as for short power outages I can plug in my small 2,400 watt suitcase size inverter easily).

Perhaps the inverter in the MEP83A is not capable of running an imbalanced load when in the 240V mode - I looked through the TM and I could not find anything that discusses how the loads should be applied in the 120V or 240V modes.

 

[LuckeyD]

The insides of the A8 were Proprietary when I was working so I have nothing to assist on this one. Maybe another member was able to get in-depth info.

 

[2Pbfeet]

I have not yet taken anything apart - but I did a bit of experimenting to see what happens to trigger the shutdown and over voltage fault.

In the 120V mode there is no issue, and I can power 120V appliances without any problem. I can plug in a 1,500/1,800 watt heater, a 500 watt light and a big furnace fan and they run just fine.

When I switch to the 240V mode I can run all of the above listed appliances fine - as long as I keep the loads somewhat balanced on each leg. I can run the 1,800 watt heater on one leg, and the blower and light on the other leg. If I can keep the legs within 1,000 watts of each other the Fault is not activated and the generator keeps running. If I have the heater set on 1,500 watts and unplug the fan and only the 500 watt light is on the other leg - then the fault triggers and the generator shuts down.

This is a problem for me - as my intended use is to connect this MEP831A to my 240V generator hook up for my house if we get into an extended power outage. As the appliances in my house turn ON/OFF, there is no way to control the potential imbalance of the loads. It is not unusual for one leg of our house to require 2,000 watts if the fridge and freezers come on at the same time - while the other leg is only running some lights. (It is a bit convenient to have the fridge and freezers on the same 120V leg, as for short power outages I can plug in my small 2,400 watt suitcase size inverter easily).

Perhaps the inverter in the MEP83A is not capable of running an imbalanced load when in the 240V mode - I looked through the TM and I could not find anything that discusses how the loads should be applied in the 120V or 240V modes.

My recollection is that the 831 is that it does have limits on each leg. If this is your planned use case, you might look into putting the generator in 120V mode, and adding an autotransformer to generate the two legs from that as that would enable any distribution of load across the two legs. (Or move up to a larger generator...)

All the best,

2PbFeet

 

[kloppk]

From my experience an imbalanced load should be fine. Each not exceeding 1.5 kw.
The Inverter actually has two 1.5 KW inverters inside.
In 240 mode one powers L0 to L1 and the other L0 to L2.
In 120 mode the inverters are synchronized and get connected in parallel by a relay inside the inverter feeding both L1 & L2.