MEP-003a No voltage

[Guyfang]

It doesn't seem very clear, but to me it sounds like I just disconnect those four connectors and test.

Indeed, that's what it sounds like to me. The wires from terminals 1&2, 3&4 and 5&6 go to the S6, AND TB2. From TB2 the wire go to the main gen, through J-9 and J-10. If those plugs are also disconnected, then the L1 should be isolated.

Having said that, can one of you tell me what the L1 has to do with excitation? The gen set excitation is accomplished by S1. Pin 27. When the main gen has been lit off by applying 24 volts to S1-pin27, then the A1, VR is supposed to take over. Judd has told us that the gen set produces no voltage, it never gets excited. That's why I wanted him to measure VAC at pins 1&2 on the A3, Freq transducer, DURING START UP. As long as S1 is held up, voltage should go to F1 and F2, and if the exciter circuit is good, the set should produce VAC. Or am I wrong here? Am I missing something?

The L1 is hooked up to the S6, Voltage selection switch. S6 also has nothing to do with Excitation. It still sounds like L1 is not within specs. But I still do not see the correlational between L1 and excitation.

 

[juddspaintballs]

I really don't know. I'm learning as we go here. I just want my generator working again and I'm following directions from more knowledgeable people.

 

[jamawieb]

It doesn't seem very clear, but to me it sounds like I just disconnect those four connectors and test.

Indeed, that's what it sounds like to me. The wires from terminals 1&2, 3&4 and 5&6 go to the S6, AND TB2. From TB2 the wire go to the main gen, through J-9 and J-10. If those plugs are also disconnected, then the L1 should be isolated.

Having said that, can one of you tell me what the L1 has to do with excitation? The gen set excitation is accomplished by S1. Pin 27. When the main gen has been lit off by applying 24 volts to S1-pin27, then the A1, VR is supposed to take over. Judd has told us that the gen set produces no voltage, it never gets excited. That's why I wanted him to measure VAC at pins 1&2 on the A3, Freq transducer, DURING START UP. As long as S1 is held up, voltage should go to F1 and F2, and if the exciter circuit is good, the set should produce VAC. Or am I wrong here? Am I missing something?

The L1 is hooked up to the S6, Voltage selection switch. S6 also has nothing to do with Excitation. It still sounds like L1 is not within specs. But I still do not see the correlational between L1 and excitation.

Looking at the schematics your right Guy, L1 does not effect the exciter but I had one unit that took me 6 months to diagnose and the last part left in the output box was L1. I didn't believe that would have anything to do with the problem so I never tested it until I ran out of options. It tested bad and after a new one was installed, voltage was returned and the unit was back up and running. I replaced the VR first but it didn't work, then I tested CVT1 and it was bad so I replaced that, still had no voltage. So that finally lead to L1. In an earlier post I said I'm not saying its not the VR but need to check everything before throwing money at the unit, that may or may not fix it.

My question wouldn't it be better to test voltage on TB5-5 while starting, that is the first location before going to the VR, A3, etc. I say this because if T1 is bad it will read no voltage at A3. That way you would know the S1 switch was working and it the CR2 diode was good if you started at TB5-5?

 

[Guyfang]

I think that's a sound plan. And not hard to do.

 

[Triple Jim]

If you want to be sure the regulator isn't the problem you can disconnect the wire from terminal 17 of the regulator and with everything else is working as it should, running the generator should produce higher than normal voltage, like 170-340 volts. This is because the regulator works by reducing the output voltage when it's too high, as opposed to many other systems that have the regulator produce exciter current. If you don't get high voltage with this test, something else is wrong.

When you disconnect that wire, tape the end so it doesn't touch anything.

 

[juddspaintballs]

My question wouldn't it be better to test voltage on TB5-5 while starting, that is the first location before going to the VR, A3, etc. I say this because if T1 is bad it will read no voltage at A3. That way you would know the S1 switch was working and it the CR2 diode was good if you started at TB5-5?

I'll figure out where TB5 is and test voltage at TB5-5 while starting. It should be easy enough to find at this point. Am I testing it as AC or DC voltage? I'm guessing AC. I'm thankful you guys can understand the wiring diagrams better than I can and know a lot more about these units than I do.

If you want to be sure the regulator isn't the problem you can disconnect the wire from terminal 17 of the regulator and with everything else is working as it should, running the generator should produce higher than normal voltage, like 170-340 volts. This is because the regulator works by reducing the output voltage when it's too high, as opposed to many other systems that have the regulator produce exciter current. If you don't get high voltage with this test, something else is wrong.

When you disconnect that wire, tape the end so it doesn't touch anything.

If I'm getting no voltage now, would that test still work?

 

[Guyfang]

At TB5-5, will be more or less 24 VDC. If you get nothing, go to A1, (relay assembly) and measure at pin 7. If no voltage, go to pin 8 on the A1. If no voltage, go to TB4-10. If no voltage, go to the S1, pin 27. if you have no voltage at pin 27, on the S1, the S1 is bad.

If you want, you can start at the S1 and work towards the TB5-5. I would do it that way, but its not written in stone to do so.

Between A1-7 and A1-8 is a diode. If you have 24 VDC on pin 8, and none on pin 7, the diode is bad.

Look at the A1 for burns and or other problems.

 

[juddspaintballs]

When cranking (only), I have ~21v DC at S1 pin 27, TB4-10, A1 pins 7 and 8, and TB5-5. Prior to cranking, there is no voltage at those locations and after the generator is running, there is no longer voltage at those locations. As the motor is just starting to run, the voltage at those locations jumps to about 27v DC for a brief moment before the voltage goes away. I'm guessing that's because the VR is now taking over.

 

[Triple Jim]

If I'm getting no voltage now, would that test still work?

That's the whole point... if the regulator is what's causing no output, then disconnecting it will make the voltage go high. It's not a common failure of the regulator, but I've seen it happen if the output transistor fails shorted.

 

[juddspaintballs]

Ok, thank you for that clarification. I'm waking up in 5 hours to go to work for 48 hours. I won't be home much on Sunday and I work again Monday. I'll try to find the time to do that check on Sunday.

 

[jamawieb]

When cranking (only), I have ~21v DC at S1 pin 27, TB4-10, A1 pins 7 and 8, and TB5-5. Prior to cranking, there is no voltage at those locations and after the generator is running, there is no longer voltage at those locations. As the motor is just starting to run, the voltage at those locations jumps to about 27v DC for a brief moment before the voltage goes away. I'm guessing that's because the VR is now taking over.

Your test are spot on. But you should continue to see voltage even after its started. One of the features of the unit is to be able to excite the field after its up and running. It does that with the start switch in the start position pin 27. So if the unit ever starts and you see no voltage, you can move the master switch back to start and excite the field. I wouldn't worry to much about that now because it should still excite the field since you have voltage. Try TripleJim's suggestion on the VR and removal of connection 17.

 

[juddspaintballs]

I disconnected terminal 17 at the voltage regulator. I had zero volts AC at the convenience outlet or the output lugs. I closed it up to come inside to tell you guys this, assuming that meant my VR wasn't the issue. Then, I looked down and saw that I had forgotten to reconnect all of the plugs on the outside of the AC output box. I reconnected them and then went back to the VR to disconnect terminal 17 again. As I did that, I dropped the screw and it rolled to the back corner of the box behind a wire bundle. As I fished it out, I found two small nuts as well. Gee, I wonder where those go? I looked around for a while, moved wires, and then noticed that the K3 had two ring terminals on the studs but no nuts holding them down. I secured the nuts down on the studs with the ring terminals firmly in place.


I went on to test the VR with terminal 17 disconnected. I suddenly had 175v AC at the convenience outlet and the AC voltmeter on the generator read nearly 300v. So, I put the terminal back in place and started the generator again. 240v AC on the generator's voltmeter, 120v AC at the convenience outlet, and 120v on both L1 and L2 when read against L0. 60.05 Hz on the Fluke and in the 60 Hz range on the generator's gauge. I stopped and started it several times with the same results.



Success? Would the two loose connections at K3 (crank relay) really cause all of my problems? Again, I'm not great at reading the manuals to understand exactly how everything works. The schematic on top of the generator shows only two connections to K3, but I have four connections on mine. The two yellow ring terminals were the loose ones. I went through and tightened every single connection in that box after that. I'm finding it hard to believe that a loose connection at the crank relay would be why I wasn't getting output, but maybe someone can explain why this is. Or maybe it's a dreaded intermittent problem.

 

[Guyfang]

What two terminals on K3 were not connected right?
Were the wires on the terminals? Or maybe laying on the control panel cabinet?

 

[juddspaintballs]

The two with yellow ring terminals in the picture above.

 

[juddspaintballs]

The wires were on the studs. They just didn't have anything holding them on tight.

 

[Triple Jim]

I don't see how those non-fastened terminals could do anything other than prevent the starter motor from running.

 

[juddspaintballs]

Me either

 

[Guyfang]

The K3 has two terminals, A1 and A2. They are for the starter Sol.

the other two wires are X1 and X2. Those two wires are to close the K3. One of the wires goes through a TB, and ends up at S1.

The two wires with yellow terminals, were A1 and A2. They definitely had something to do with start problems. I want to look at the schematics in the morning. It's 01:30 here.

 

[Guyfang]

Just a thought. But loose terminals cause heat, pump the draw up on the battery durring start. Could that have put enough draw on the battery's to not allow the set to self excite?

 

[juddspaintballs]

The plot thickens. I went out and started it again. Frequency went right to 60 and remained. Voltage went over 300 on the gauge. As I walked down to the garage to get the Fluke, I heard the tone of the motor change a couple of times like it slightly loaded, and then went back to normal. Nothing is hooked up to this generator, by the way. When I made it back, I had no frequency or voltage. The convenience outlet read 0.43v.

I popped the cover open and disconnected terminal 17 on the VR. I started the generator and it had over 300 volts on the gauge and about 173 at the convenience outlet. I reconnected terminal 17 and had no voltage on the gauge and 0.43 volts on the Fluke at the convenience outlet.