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Hank F.
Hank F., Technician
Category: Small Engine
Satisfied Customers: 14560
Experience:  Certified on Onan and Generac generators
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My portable generator (6200 watts) runs, but does not put out

Resolved Question:

My portable generator (6200 watts) runs, but does not put out any electricity. Can you give mw advice on where to look to fix?
Submitted: 4 years ago.
Category: Small Engine
Expert:  Hank F. replied 4 years ago.
Hello!
Thank you for choosing Just Answer for the solution to your problem.
My name is XXXXX XXXXX I am going to assist you with this.

I can help walk you all the way through troubleshooting - I just need the model number of the genset.
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Customer: replied 4 years ago.
It says Troy-bilt 030432
Expert:  Hank F. replied 4 years ago.
Cool. This is a very easy set to troubleshoot.

What I need you to do first is this:

Remove the vented end cover from the genset.

Gain access to the Power Regulator Board (PRB).

There are 4 wires – 2 go to the brushes (numbers 1 and 4), and the other 2 come from the exciter winding (numbers 2 and 6).

Disconnect the brush wires. Pay attention to which wire goes to which brush.

Make up 2 jumper wires that will attach to the brushes, with a 5A fuse in one of the jumpers.

Connect the fused jumper to the positive (outer) brush and to the positive terminal of a 12V battery.

Connect the other jumper to the negative (inner) brush, but do not connect it to the battery at this time.

Gain access to the exciter wires.

Start the set, and connect the negative jumper to the negative terminal of the battery.

Set your meter to VAC and measure the AC output at the receptacle of the set. It should be a minimum of 60 volts.

Test the voltage across the 2 exciter wires. There should be a minimum of 60VAC.

How much voltage is there?

Set your meter to VDC and test the voltage at the brush wires that come from the PRB. Make sure you connect the positive lead to the positive wire. You should see at least 10VDC.

Disconnect the jumpers from the battery and shut the set down.

How much voltage is there?

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Customer: replied 4 years ago.
Would it help if I told you I already tried replacing the PRB (I assume you mean the small plastic circuit board)?
Expert:  Hank F. replied 4 years ago.
The PRB is the Power Regulator Board - the small plastic board.

But no, it won't help.
The test I gave you bypasses the board.
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Customer: replied 4 years ago.
I have hooked up the jumpers, but there are 4 wires to the exciters, two red and two blue. One red says 22A and the other says 90 on the insulation. One of the blues looks like it says 240 or 260 and some other stuff.
Expert:  Hank F. replied 4 years ago.
I have never seen them marked like that before - even the schematic does not show that.

But the 22A is a voltage sense circuit, and exciter wires are almost always blue or yellow.

Measure the voltage at both the red and blue, just to be safe - one lead on each red wire, then one lead on each blue wire.
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Customer: replied 4 years ago.
I get 118 volts at the 4 120 volt outlets, and 116 off the two exciter wires I tried.
Customer: replied 4 years ago.
By the way I goofed, I did one red and one blue exciter wire
Expert:  Hank F. replied 4 years ago.
You have to measure across the 2 reds, then across the 2 blues.
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Customer: replied 4 years ago.
188 v across the reds, 15.5 across the blues
Customer: replied 4 years ago.
I tried to send you a picture f the unit and wires, did you get it?
Expert:  Hank F. replied 4 years ago.
No, I did not.

To upload a photo, use the paper clip icon at the top of the reply box.
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Customer: replied 4 years ago.
Expert:  Hank F. replied 4 years ago.
Wow - I have never seen the colors mixed like that before.

Let me do a bit of research on this.
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Customer: replied 4 years ago.
The wires are all red and blue, the grey wire across the front is one of my jumpers
Expert:  Hank F. replied 4 years ago.
Yes, but usually the 2 wires at one end of the board will be one color, while the 2 wires at the other end of the board will be a different color.
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Customer: replied 4 years ago.
The connectors on the right are different from all the rest, maybe a bit heavier duty. but the connector types are all in matching pairs
Expert:  Hank F. replied 4 years ago.
I see that.

Can you recheck the numbers on the blue wires, and possibly get a picture of the other ends of the wires?
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Customer: replied 4 years ago.
This is weird. the numbers are the same (15.5) when I use autorange, but if I use AC I get 140 and if I set it to Dc I get 59 volts

I am using a Fluke by the way
Customer: replied 4 years ago.
Expert:  Hank F. replied 4 years ago.
No, not the voltage - the numbers stamped on to the wires.
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Customer: replied 4 years ago.
The blue on the left has an 11A on it and the right one has a 2

Another picture coming
Customer: replied 4 years ago.
Expert:  Hank F. replied 4 years ago.
So the wires on the left are 11A and 22A, as I had described (11A is an off shoot of 11). These are the voltage sensing wires
The other side is #2, as I had described, and the other should be 6 - these are the exciter wires.
But either way, by jumping 12V to the brushes, and you got 118V at the receptacles, it tells us that the rotor and stator are just fine.
That means that the new PRB is bad.

Here is a brief description of how the genset operates, to help you understand this:

A genset is composed of 2 major components – an engine and a generator, commonly referred to as an alternator. hf

A generator is composed of 2 major components – a rotor, commonly referred to as an armature, and a stator. The stator typically has 2 or more windings – 1 or more power windings, and a smaller exciter winding.

There are 3 things required for the production of electricity – a magnetic field, a conductor (wire), and movement between the field and conductor. Since the field has no physical mass, it is much easier to move it than to move the conductor. We move the field by spinning it with the engine. This is why most gensets are known as revolving field gensets.hf

When you start the engine, the rotor starts spinning (it is connected directly to the crankshaft of the engine).

The rotor is a giant electromagnet.

When not running, the rotor retains a small bit of magnetism, known as residual magnetism.

As it spins, the magnetic field around the rotor is passed through the windings of the stator (conductor). The magnetic field aligns the electrons in the wire and makes them move. This flow of electrons is electricity. Residual magnetism will create a residual output voltage of about 3-6 VAC at the receptacles.

However, the amount of electricity flowing is not very much, so the PRB takes the AC power coming in from the exciter winding and converts it to a DC current, and feeds it back to the rotor through the brushes. This increases the strength of the magnetic field – which, in turn, increases the amount of electricity produced – until the PRB senses that there is 120 volts (give or take) available.

Remember, a magnet has 2 poles – north and south, or positive and negative. As the positive pole passes the windings, it moves the electrons in one direction (the positive pulse). As the negative pole passes by, it moves the electrons in the opposite direction (the negative pulse). One positive pulse and one negative pulse are one cycle, or Hertz. Since US power is 60 Hz, this process must happen 60 times per second (50 times per second (50 Hz) in much of the world).hf

We now have nominal voltage flowing (120 V in the US).

When a load is applied to the genset, this voltage drops correspondingly to the size of the load.

The PRB senses this power drop from the exciter winding and says ‘Hey, I’ve got a load on and the power is dropping. I’d better make more power’. It does this by increasing the DC voltage to the rotor, which creates a stronger magnetic field, which pushes even more electrons into movement.

The VR constantly monitors this voltage and adjusts the field accordingly.

We now have electricity.hf

Customer: replied 4 years ago.
So I replace the PRB and get another bad one? Can something be trashing them?
Expert:  Hank F. replied 4 years ago.
Except for connecting them wrong, not likely.

But you have seen that the generator will produce power if it gets juice to the field (rotor).
That is the purpose of the PRB - to send juice to the field.
Customer: replied 4 years ago.
Is there a way to check that I am not making the connections wrong?
Expert:  Hank F. replied 4 years ago.
I an upload the wiring diagram for you, if you know how to read one.
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Customer: replied 4 years ago.
If thats the best we can do. I guess my question is do I have the red and blue wires reversed? Thats the only thing I can think of
Expert:  Hank F. replied 4 years ago.
I can't say for sure.
The schematic will not tell you that.
But I do know that on some PRB's, it does make a difference.
Customer: replied 4 years ago.
Will switching trash it, or can I try switching?
Expert:  Hank F. replied 4 years ago.
You can try switching - it is actually one of the troubleshooting steps.
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