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I need electronic help!!!!!  What is this? (Read 125 times)
Dave
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Re: I need electronic help!!!!!  What is this?
Reply #15 - 12/05/25 at 16:44:47
 
I have found a person who knows what that little black device is...and he actually has some (however he has just moved and they are packed away in a box somewhere).  He has successfully repaired these Fault Modules using them.

The device is an SCR - Silicone Controlled Rectifier.

This is the definition of an SCR:

An SCR, or Silicon Controlled Rectifier, is a solid-state electronic switch with three terminals: an anode, a cathode, and a gate. It acts like a diode that can be turned on and off, conducting current in only one direction when a trigger signal is applied to the gate.

So it appears that I have found a source......someday when he is unpacked! Smiley
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MMRanch
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Re: I need electronic help!!!!!  What is this?
Reply #16 - 12/05/25 at 20:55:07
 
Like I've been saying for years .... That Dave can fix anything  !   Shocked

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Dave
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Re: I need electronic help!!!!!  What is this?
Reply #17 - 12/06/25 at 15:52:54
 
MMRanch wrote on 12/05/25 at 20:55:07:
Like I've been saying for years .... That Dave can fix anything  !   Shocked



I hope you are right!!!! Huh

I believe the needed repairs to this generator are pretty minor and limited to replacement of a few "plug and play" components.  The Governor Control unit are known troublemakers - the Fault Modules do go bad occasionally.  I believe all of this stuff worked pretty well when it was new - but a lot of it has been shipped around the world and stored outdoors for the last 20+ years.  A lot of the equipment may show low use on the hour meter - but it may have gone through something called a "reset" where the equipment is rebuilt with new components and put back in service.

I am just hoping to get small, reliable and efficient 3KW diesel backup generator out of this.

Last year I bought and worked on a 5KW version that weighs 800 pounds and has a 2 cylinder diesel engine.  It needed the fuel tank cleaned out and some leaky fittings replaced, new fuel and injector return hoses, new filters, a new fuel tank sender and fuel gauge - and an outlet added to supply 50amp 240 volt service.  This generator now works really well - but it is a bit big for what we need.


All this is new to me - thankfully there is a forum called Steel Soldiers that deals with all the government surplus equipment and vehicles.

This is what the wiring looks like in the engine compartment!
 
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Dave
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Re: I need electronic help!!!!!  What is this?
Reply #18 - 12/21/25 at 08:54:00
 
I was able to install the new Governor Controller and  an outlet on this generator, and give it a 30 minute test run under a 2,000 watt load.

It is running great and will keep us in power if we have a grid failure anytime soon.

I also found the part I need to fix the Fault Monitor.....I think I can afford to buy the part as it only costs 41 cents!

https://www.digikey.com/en/products/detail/stmicroelectronics/X00602MA-1AA2/1...
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Re: I need electronic help!!!!!  What is this?
Reply #19 - 12/22/25 at 19:06:24
 
GREAT Dave !  

You may have gotten out with more Generator , for less money that we did !  


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Dave
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Re: I need electronic help!!!!!  What is this?
Reply #20 - Yesterday at 04:09:22
 
MMRanch wrote on 12/22/25 at 19:06:24:
GREAT Dave !  
You may have gotten out with more Generator , for less money that we did !  


I am sure you paid less money for a new gasoline generator.

Finding a good reliable "diesel" generator that is affordable is a challenge.  A new 5,000 watt diesel generator is about $4,500 for a basic open frame generator....even before you pay tax and shipping!  These surplus military generators are anywhere from $400 - $2,600...just depends on who has them and if they are working or not.  When you get them from GovPlanet they often are not working and have been sitting outdoors for years.  Lately it seems that folks are bidding way too much for these "projects" and have driven the prices up....they are all going to need hours of work to become running and reliable generators.   Some folks buy them and discover the work involved to get them running again is a bit beyond what they can do....and they come up for sale on Facebook Marketplace.

The used market has a lot of old diesel generators that are in questionable condition - and a lot of them are just too big for use at my home.  Gas generators are pretty forgiving about being run at low wattage and they can vary the load without issue - diesel engine generators don't like being run at less than a 50% load for extended periods - it is best to run them at loads 60% or more.  If you run a diesel generator without making it work - the exhaust "wet stacks" and gets filled with an oily goo that can eventually turn into a thick carbon that clogs up the exhaust header and muffler.

My reason for wanting a diesel generator is that I have a 270 gallon diesel tank for use in the tractor and zero turn mower - so that provides me with a large supply of fuel for a diesel emergency generator.  This 3KW diesel generator runs 2-3 hours on a gallon of fuel (depending on load) - so I likely could run the generator continuously for 20+ days with the fuel I have on hand.

These surplus military generators have been sitting around for 15-20 years and they need work when you get them.  They claim to have all the fluids  drained - but there is a goo build up in the tank and they need to be cleaned.  The fuel sending units have often gone bad and need to be replaced, the rubber fuel lines are old and cracked, filters need to be changed.  The original 24V batteries are available from places that provide them for aircraft and they are expensive - so most folks replace them with a pair of smaller 12V batteries from lawn tractors or motorcycles.

I believe this one I bought had a wiring issue and when it failed to operate properly (bad Fault Module) - the Government set it to the side and abandoned it.  The owner I bought it from said it had 2 hours on it when he bought it - he had disconnected the Fault Module and used it without the generator having the ability to shut itself down if it overheated or was overloaded...or lost oil pressure.  I hope to get the Fault Module repaired and operational - I am still chasing down the reason it overloads and damages them.....i believe there is something wrong with the K12 Shut Down relay, and when the module tries to shut the engine down the relay is sending too much current to the Fault Module and melts the circuit board components.

Seems like I always get myself into a new mechanical/electrical challenge!!! Huh


This fellow restores Onan generators and had a Wet Stacking experience.

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« Last Edit: Yesterday at 07:03:13 by Dave »  

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Dave
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Re: I need electronic help!!!!!  What is this?
Reply #21 - Yesterday at 16:29:28
 
Today I learned something more about electrical systems, and I have discovered why this generator burned up the Fault Monitor circuit board.

All of the circuits and senders that report on the condition of the Oil Pressure, Engine Temperature and Voltage/Current overloads tested just fine.  The problem did not seem to be caused by the monitoring system - but seemed to be caused when the Fault Module tried to energize the Engine Shut Down circuit.  It also seemed to be a problem not of too much voltage - but too much current.

I used my Ohm meter and checked the circuit from Pin5 at the Fault Module to the S1 switch that provides power to the K12 relay circuit that is responsible for shutting down the engine when the Fault Module tells it to. The test showed "0" resistance....which didn't seem right to me. If the circuit has no resistance, then the amperage is only limited by the capacity of the battery!  The wires in this circuit are very small and could not handle anything approaching 1 amp!

Next I used the Ohm meter to test across terminals 13-14 at the K12 relay. Again there was "0" resistance.

Next I removed the relay and tested across the terminals 13-14 - I got a resistance of 686 ohms. Now that resistance would result in a current of 0.04 amps and are getting somewhere.

I then started to investigate this little Diode looking thing that was attached to the same terminals 13-14.  I had no idea how to test it - the wiring diagram listed it as TVS4.

I posted this on the Steel Soldiers forum, and a few hours passed and a fellow from Germany told me it was a Transient Voltage Suppressor and that they sometimes go bad.  The purpose is to dampen voltage pulses in the line so the relay operates smoothly.  He said to test it and make sure it was neither fully "open" or "closed"..mine tested fully closed.

I removed TVS4 and checked across terminals 13-14 - it was now an "open" circuit where with the TVS4 installed it was a closed circuit (The bad TVS4 was acting like a small jumper cable).

I reinstalled the K12 relay and checked the resistance from Pin 5 at the Fault Module to switch S1 (which was previously "0"), and now that the TVS4 is removed it measured 686 ohms!!!!!!!

So it appears the TVS4 has gone bad!!!!

I have ordered a replacement and as soon as it arrives I will put it in...and I believe the Fault Module will survive from now on!!!!!
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Re: I need electronic help!!!!!  What is this?
Reply #22 - Yesterday at 19:13:57
 
 Diode looking thing that was attached to the same terminals 13-14.  I had no idea how to test it  

Diode , electrons from volt meter ( or any source ) flow one way freely , but not the other direction.    DC electrons flows : Negative to positive direction.
So
Zero resistance in one direction but really BIG resistance the other direction.

Look up AC to DC with Diodes , to see the 4 diode  connection pattern for flat line DC ... might be the picture to see ?

I'm sure you will win over a silly machine !  

Dad used to say : "Well  son , somebody else figured out how to build and  make it work ... SO ... Can't you at least look at it and figure what they did !   Huh
I think " MOST - OF - TIME - YES "  is the  BEST assure  Wink

..............

Completed the 18months course in Industrial Electricity after my military time , but never worked in that field ... I went on to College for 2 yr. degree in energy engineering finished it , but never worked in that field either ... I got a Job as a government employee to pay my way in school then kept the Federal Civil Servant Job. (The Bird-in-the-hand ) thing.   Smiley
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Dave
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Re: I need electronic help!!!!!  What is this?
Reply #23 - Today at 01:53:32
 
MMRanch wrote on Yesterday at 19:13:57:
 Diode looking thing that was attached to the same terminals 13-14.  I had no idea how to test it  


MM:

The fact that it looked like a diode didn't mean it actually was one, that is why I was unsure how to test it.  The body of the thing did not have a symbol that showed the current direction the way a real "diode" would, and the symbol in the wiring diagram for the TVS4 did not show a diode symbol either....and it labeled it a Transient Voltage Suppressor....therefore I was not sure how to test it as it didn't seem to be a diode (even though the physical appearance resembled one).

It turns out that it can be tested similarly to a diode - if the ohm meter shows it as "0" resistance in either direction - it is bad.  Evidently it can be installed in either direction - they don't care which direction they are installed.

 I have attached a photo of the wiring diagram that shows the symbol for the relay K12 that operates the engine shut down, and TVS4 which is the Transient Voltage Suppressor.  (The TSV is used to stabilize the relay and reduce "chatter" that might occur if the voltage is not steady).  
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