MEP-806B control board for fuel solenoid and excitation - assistance request

[bimota]

So we are trouble shooting the board that control the fuel solenoid relay and also excitation. Our engine runs well when we bypass the control board for the fuel solenoid but we lack the DC power light, solenoid connection and excitation.

Attached are photos of the board and a tag - can anyone ID the tag and meaning?

 

[Guyfang]

If you look at TM 9-6115-672-24P, you will see that the top number is the Part number for the Backplane Module. The bottom number looks to me like a location number, from the last supply facility that stored the Backplane, before issue.

If you do not have the proper manuals for this gen set, they are available in the TM download section of SS.

Have you ever seen this gen set run properly? Is it new to you? Or has if failed during operation?

 

[Chainbreaker]

Also, since its a backplane board it would make sense that it has a lot of I/O connections. If you haven't already, I would remove all the connectors and clean all the contacts with an electrical contact cleaner (DeOxit). Who knows, You might get lucky!

 

[bimota]

So we have the engine cranking and starting by cleaning connections; runs fine and the governor and other green lights are on except for Field Sense, the AVR does not seen to light up and excite nor maintain power. The other issue is the digital display back light is not lighting up the screen, so we can barely see the display.

The manual and troubleshooting a little unclear on excitation, and field sense. My mechanic wants to replace Backplane Module which does not look available on eBay though I know there are MEP-806b beind parted out. Anyone have a clean Backplane Module or knowledge about excitation work arounds?

 

[Guyfang]

There is no workarounds. Having said that, please refer to my questions in message #2. I am pretty good with these sets. so it helps if I have a little bit more info.

 

[bimota]

This is new unit to us just purchased at auction. We have a customer that wants to use it for wood mill and we need to get it running properly.

On some generators you can manually do excitation to get the field sense voltage and see if the AVR starts and the alternator produces power, that would be great to try to then know it is an excitation issue not a larger issue.

We are working on it today - what can you advise? Can we call you?

 

[Guyfang]

If you dont mind calling germany, yeah, you can call. But lets try this for the time being. Tell me what it is doing, and what its not doing.

 

[bimota]

I'm pleased to say with just your encouragement - we got it to work! Basics, like holding the start switch longer for the excitation to take place after the speed switch is up to speed. Only with Military units do regular generator technicians say they are burnt up because they don't know to hold the start switch down for well after they start and run. Typical commercial units would grind the starter...LOL

 

[Guyfang]

Well, that was one of the things I was going to ask you about. Its a VERY common "failure". We have be indoctrinated to not turn a starter over too long. The MPU on all the TQG's will prevent the starter grinding. You can damage the gen set by holding it up too long. or if the AC volt regulator is bad. That's the reason all of the TQG's have a MWO to add a fuse in series with the excitation system to keep that from happening. I also wanted to remind you that if you do need a backplane, you should include all model numbers of the 806B family, AND the 805B. Reason being, both sets use the same part, and as it doesn't have a UOC, it compatible to the 400 hertz models also. Glad you got it up. If you have any questions, just shoot me a PM.

Take care,

Guy Wiltfang