MEP 802A M8 Percent Load Gauge Issue

[loosegravel]

I finally found the picture of the insides of the Current Transformer that I mentioned above.
View attachment 886216

That’s very interesting. With no moving parts, it makes one wonder what could cause an intermittent open? Maybe loosen all 6 of the studs, clean and tighten? Treat the studs with some corrosion prevention like WD-40?

 

[CallMeColt]

That’s very interesting. With no moving parts, it makes one wonder what could cause an intermittent open? Maybe loosen all 6 of the studs, clean and tighten? Treat the studs with some corrosion prevention like WD-40?

In my case, there never was an open. Everything tested as it should have. It makes no sense really. I don't know what else could interfear with it's operation as I'm not sure exactly how it does, what it does. Maybe chunks of rust stuck to the windings?

 

[Guyfang]

Only one way to find out. I do know that the nuts are sometimes really hard to take off, and you can snap off a feed through screw, just like over tightening them. Tight is good, but Man Mountain Dean tight is not good.

 

[Ray70]

The only thing I can think of is corrosion between the studs and wires or a bad connection between one coil wire and the inner half of it's stud ( can't tell from picture how those connections are made ) I've seen this same issue but on an 002 in which the problem was some corrosion inside the big AC select switch, but the result was the same... AMP readings about 1/2 what they should have been.
So I definitely think you have corrosion somewhere causing high resistance at a connection.
Like Guy said... only one way to find out!
And fear not, if you break it worse than it already is, I have a spare available.

 

[CallMeColt]

It's working for now, so I am going to focus on the other issues with the unit. I have a spare that I need to test as well.

 

[loosegravel]

Just a thought here. I've been working on an 804A unit which has some high resistance issues in the J5/P5 and J6/P6 AMP connectors. I've ordered some socket pins to repair the 24-pin connector. These problems have been affecting the 24vdc power up to the main control panel, the start circuit and also the electronic governor control circuit. I was just looking at the schematics for the 802A unit. I'm seeing that this unit also has some of the same bulkhead style through connectors. It seems that when the upper panels on these units are not properly secured and sealed, we can get water intrusion into these connectors because of the way that they're mounted vertically. It may be a good place to check. You may find some loose pin sockets like I did.

 

[loosegravel]

Just a thought here. I've been working on an 804A unit which has some high resistance issues in the J5/P5 and J6/P6 AMP connectors. I've ordered some socket pins to repair the 24-pin connector. These problems have been affecting the 24vdc power up to the main control panel, the start circuit and also the electronic governor control circuit. I was just looking at the schematics for the 802A unit. I'm seeing that this unit also has some of the same bulkhead style through connectors. It seems that when the upper panels on these units are not properly secured and sealed, we can get water intrusion into these connectors because of the way that they're mounted vertically. It may be a good place to check. You may find some loose pin sockets like I did.

 

[loosegravel]

View attachment 886234View attachment 886234

The pin size on these connectors is .062". I've been using the shank end of a .060" drill bit to check the sockets for tightness. If I don't feel the resistance when inserting or removing the drill bit then I'm going to replace that socket. I'm not seeing any problems with the pins, only the sockets.

 

[CallMeColt]

The pin size on these connectors is .062". I've been using the shank end of a .060" drill bit to check the sockets for tightness. If I don't feel the resistance when inserting or removing the drill bit then I'm going to replace that socket. I'm not seeing any problems with the pins, only the sockets.

Intresting. I checked the J6 and it looked okay, but didn't think about if the connector pins were loose. Maybe my hitting the unit made it make better contact? Good tip and it's a fairly easy check.

 

[Farmitall]

I finally found the picture of the insides of the Current Transformer that I mentioned above.
View attachment 886216

Excellent picture!!

Thank You for finding it and posting. It adds some meaning to the schematic and illustrates the simplicity of a "sampling circuit".

 

[Guyfang]

Part of the problem is pressure washing, and the other part is that the plugs are often not tight. I love pressure washing. But when done, and I always tried to do it when it was warm, if not hot. Or, leave the gen set in a warm building for a few days. I know, this is not always an option. Also, using compressed air on both halfs of the plug, after washing. Using some type of contact spray is always a good idea. Even WD-40.

 

[Farmitall]

View attachment 886234View attachment 886234

For cleaning things like this I cut bristles of an acid brush a bit shorter to stiffen it up a little and use some electronics contact cleaner spray or just 90% isopropyl and compressed air.

 

[sjc]

Looking at the photo of the dis-assembled unit from Kurt, it looks like the CT secondary wires are soldered to the thru connectors ... most likely you have a dry solder joint if that is the case.