Generac 7500
 

I bought this generator a few weeks ago, used. It worked fine, but
stopped putting out any power. I contacted repair people, the local
repair facility only works on bigger units, but the man said it was
most likely the voltage regulator. Got the regulator on line and
installed it, I get power now. The 120v recepticles put out 50 v. and
the 220 put out approx. 120v. Any ideas, suggestions, referals? Thanks.

Generac 7500
 

wrote in message
oups.com...

I bought this generator a few weeks ago, used. It worked fine, but
stopped putting out any power. I contacted repair people, the local
repair facility only works on bigger units, but the man said it was
most likely the voltage regulator. Got the regulator on line and
installed it, I get power now. The 120v recepticles put out 50 v. and
the 220 put out approx. 120v. Any ideas, suggestions, referals? Thanks.

1 The new regulator is faulty.
2 You installed it improperly.
3. Something else is wrong with it.

Generac 7500
 

Are you sure your engine is up to speed? Check the throttle
and governor first.

wrote:
I bought this generator a few weeks ago, used. It worked fine, but
stopped putting out any power. I contacted repair people, the local
repair facility only works on bigger units, but the man said it was
most likely the voltage regulator. Got the regulator on line and
installed it, I get power now. The 120v recepticles put out 50 v. and
the 220 put out approx. 120v. Any ideas, suggestions, referals? Thanks.

Generac 7500
 

In article .com,
wrote:

I bought this generator a few weeks ago, used. It worked fine, but
stopped putting out any power. I contacted repair people, the local
repair facility only works on bigger units, but the man said it was
most likely the voltage regulator. Got the regulator on line and
installed it, I get power now. The 120v recepticles put out 50 v. and
the 220 put out approx. 120v. Any ideas, suggestions, referals? Thanks.

Ellombris-


I have downloaded some Generac manuals from
http://www.generac-portables.com including a couple 5500 watt units
(1314-0 and 9885-3). Both of these use the 83970, called a "System
Control Board".

The 83970 has a trim pot that sets voltage. Some models have the board
mounted with the trim pot next to a rubber plug on the left side of the
connector panel. If your model has this board, it might easily be
misadjusted. Try adjusting it for an initial value of 124 Volts output
with no load. A small adjustment can make a large difference in output!

There is also an 84132, called a "Power Regulator Board" on the diagram
and "Assembly, Drive Module, Power Regulator" on the parts list. This
module controls current to the rotating field. It has no adjustment
itself, but is driven by the System Control Board. Was that the module
you replaced?

If you study the problem further and still can't solve it, check out the
"Generators and Motors" forum at
http://www.smokstak.com.

Fred

Generac 7500
 

Fred McKenzie wrote:
In article .com,
wrote:

I bought this generator a few weeks ago, used. It worked fine, but
stopped putting out any power. I contacted repair people, the local
repair facility only works on bigger units, but the man said it was
most likely the voltage regulator. Got the regulator on line and
installed it, I get power now. The 120v recepticles put out 50 v. and
the 220 put out approx. 120v. Any ideas, suggestions, referals? Thanks.

Ellombris-


I have downloaded some Generac manuals from
http://www.generac-portables.com including a couple 5500 watt units
(1314-0 and 9885-3). Both of these use the 83970, called a "System
Control Board".

The 83970 has a trim pot that sets voltage. Some models have the board
mounted with the trim pot next to a rubber plug on the left side of the
connector panel. If your model has this board, it might easily be
misadjusted. Try adjusting it for an initial value of 124 Volts output
with no load. A small adjustment can make a large difference in output!

There is also an 84132, called a "Power Regulator Board" on the diagram
and "Assembly, Drive Module, Power Regulator" on the parts list. This
module controls current to the rotating field. It has no adjustment
itself, but is driven by the System Control Board. Was that the module
you replaced?

If you study the problem further and still can't solve it, check out the
"Generators and Motors" forum at
http://www.smokstak.com.

Fred

The unit I have is a 7500 not the 5500, and I do have a parts list and
schematic for this generator. Thank you for your advice. I spoke to a
tech for the local company that works on larger units and he told me,
the 84132 has an adjustment screw on it. That is what I'll be trying
next. My kid works nights so I won't be running the generator 'till
Sunday, his day off.
Thank you you for your help, if this works I'll post that The problem
is solved, if not I'll be begging for help again and will check out the
websute you suggested.

Generac 7500
 

In article . com,
wrote:

The unit I have is a 7500 not the 5500, and I do have a parts list and
schematic for this generator. Thank you for your advice. I spoke to a
tech for the local company that works on larger units and he told me,
the 84132 has an adjustment screw on it.

Ellombris-

My mistake. Somehow I read 7500 and thought 5500 when looking at my
collection of downloaded manuals!

Other Generac generators use the same set of boards. If yours has the
84132 module (located in the end bell of the generator, connected to the
brushes), it most likely also uses the 83970 module (located inside the
connector panel assembly). They work together to regulate voltage.

I have a set of manuals (Clymer "Small AC Generator Service Manual",
volumes 1 and 2). Volume 2 covers Generac fairly thoroughly. One
section leaves me with the impression that the 83970/84132 module pair
is used for all models that have the idle control circuit, from 3500 to
7500 Watts.

Fred

Generac 7500
 

wrote:
Fred McKenzie wrote:
In article .com,
wrote:

I bought this generator a few weeks ago, used. It worked fine, but
stopped putting out any power. I contacted repair people, the local
repair facility only works on bigger units, but the man said it was
most likely the voltage regulator. Got the regulator on line and
installed it, I get power now. The 120v recepticles put out 50 v. and
the 220 put out approx. 120v. Any ideas, suggestions, referals? Thanks.
Ellombris-


I have downloaded some Generac manuals from
http://www.generac-portables.com including a couple 5500 watt units
(1314-0 and 9885-3). Both of these use the 83970, called a "System
Control Board".

The 83970 has a trim pot that sets voltage. Some models have the board
mounted with the trim pot next to a rubber plug on the left side of the
connector panel. If your model has this board, it might easily be
misadjusted. Try adjusting it for an initial value of 124 Volts output
with no load. A small adjustment can make a large difference in output!

There is also an 84132, called a "Power Regulator Board" on the diagram
and "Assembly, Drive Module, Power Regulator" on the parts list. This
module controls current to the rotating field. It has no adjustment
itself, but is driven by the System Control Board. Was that the module
you replaced?

If you study the problem further and still can't solve it, check out the
"Generators and Motors" forum at
http://www.smokstak.com.

Fred

The unit I have is a 7500 not the 5500, and I do have a parts list and
schematic for this generator. Thank you for your advice. I spoke to a
tech for the local company that works on larger units and he told me,
the 84132 has an adjustment screw on it. That is what I'll be trying
next. My kid works nights so I won't be running the generator 'till
Sunday, his day off.
Thank you you for your help, if this works I'll post that The problem
is solved, if not I'll be begging for help again and will check out the
websute you suggested.

Hi...

Just playing the devil's advocate for a moment...

Difficult to tell where any of us are in the world, so can't
even guess at where you might be, but those just about 1/2 voltages
might not be a coincidence...

It's not possible that you're in the UK and bought a North American
regulator, is it? :)

Take care.

Ken

Generac 7500
 

Ken Weitzel wrote:
wrote:
Fred McKenzie wrote:
In article .com,
wrote:

I bought this generator a few weeks ago, used. It worked fine, but
stopped putting out any power. I contacted repair people, the local
repair facility only works on bigger units, but the man said it was
most likely the voltage regulator. Got the regulator on line and
installed it, I get power now. The 120v recepticles put out 50 v. and
the 220 put out approx. 120v. Any ideas, suggestions, referals? Thanks.
Ellombris-


I have downloaded some Generac manuals from
http://www.generac-portables.com including a couple 5500 watt units
(1314-0 and 9885-3). Both of these use the 83970, called a "System
Control Board".

The 83970 has a trim pot that sets voltage. Some models have the board
mounted with the trim pot next to a rubber plug on the left side of the
connector panel. If your model has this board, it might easily be
misadjusted. Try adjusting it for an initial value of 124 Volts output
with no load. A small adjustment can make a large difference in output!

There is also an 84132, called a "Power Regulator Board" on the diagram
and "Assembly, Drive Module, Power Regulator" on the parts list. This
module controls current to the rotating field. It has no adjustment
itself, but is driven by the System Control Board. Was that the module
you replaced?

If you study the problem further and still can't solve it, check out the
"Generators and Motors" forum at
http://www.smokstak.com.

Fred

The unit I have is a 7500 not the 5500, and I do have a parts list and
schematic for this generator. Thank you for your advice. I spoke to a
tech for the local company that works on larger units and he told me,
the 84132 has an adjustment screw on it. That is what I'll be trying
next. My kid works nights so I won't be running the generator 'till
Sunday, his day off.
Thank you you for your help, if this works I'll post that The problem
is solved, if not I'll be begging for help again and will check out the
websute you suggested.

Hi...

Just playing the devil's advocate for a moment...

Difficult to tell where any of us are in the world, so can't
even guess at where you might be, but those just about 1/2 voltages
might not be a coincidence...

It's not possible that you're in the UK and bought a North American
regulator, is it? :)

Take care.

Ken

OK ! I'm in the US and this unit worked when I bought it used, I was
wrong about the voltage regulator. I have the used one I replaced and
the screw is not to adjust the voltage, it's to secure the heatsink to
a component on the board. I looked on the side of the output panel and
found the adjustment on the 83970 and adjusted it. The most voltage I
get out of the 120 0ut is 68v and I adjusted the trim to give me 120
out of the 220 receptacle. That gives me 60v out of the 120 outlets.
This unit uses a rotor and a stator, so I can't see how it would have
fields. The original diagnostic by a friend who is an electrical
contractor was that one of the fields might be bad, therefore the 1/2
power. I read something about flashing the fields, but don't think this
applies to me. I was told by the local tech that repacement rotors and
stators are usually 2 to 3 hundred bucks, before the labor costs. It
would be nice to find a unit with a blown engine, buy it and swap out
the generator. Any more advice is welcome, and thanks to all.

Generac 7500
 

In article . com,
wrote:

OK ! I'm in the US and this unit worked when I bought it used, I was
wrong about the voltage regulator. I have the used one I replaced and
the screw is not to adjust the voltage, it's to secure the heatsink to
a component on the board. I looked on the side of the output panel and
found the adjustment on the 83970 and adjusted it. The most voltage I
get out of the 120 0ut is 68v and I adjusted the trim to give me 120
out of the 220 receptacle. That gives me 60v out of the 120 outlets.
This unit uses a rotor and a stator, so I can't see how it would have
fields. The original diagnostic by a friend who is an electrical
contractor was that one of the fields might be bad, therefore the 1/2
power. I read something about flashing the fields, but don't think this
applies to me. I was told by the local tech that repacement rotors and
stators are usually 2 to 3 hundred bucks, before the labor costs. It
would be nice to find a unit with a blown engine, buy it and swap out
the generator. Any more advice is welcome, and thanks to all.

Ellombris-

If you needed to flash the field, there would be NO output, so don't
worry about doing that.

Have you inspected the brushes to see if they might be worn down or have
a frayed wire that might be touching the frame?

A shorted battery charger rectifier diode might cause low output, but
probably wouldn't zap the 84132 module.

Some 7500 Watt Generac models had winding resistances in Ohms as
follows, per the Clymer volume 2 manual:

Rotor 7.6-9.1
Main AC Power .20-.25/.20-.25
Excitation(Dpe) 1.56-1.91
DC Battery Charger Winding .05-.09/.06-.11

The Excitation (Dpe) winding supplies AC voltage to the 84132 module,
which rectifies it and supplies current to the field via the brushes.

If you have time, visit http://www.smokstak.com. There is a search
function there you could use to find a wealth of information.

Fred

Generac 7500
 

"Ken Weitzel" wrote in message
news:zZoch.411882$R63.269149@pd7urf1no...

Just playing the devil's advocate for a moment...

Difficult to tell where any of us are in the world, so can't
even guess at where you might be, but those just about 1/2 voltages
might not be a coincidence...

It's not possible that you're in the UK and bought a North American
regulator, is it? :)

Sounds like a split 240 generator. Perhaps the regulator connections got
switched to the 240 leads instead of the 120 leads?

Generac 7500
 

Homer J Simpson wrote:
"Ken Weitzel" wrote in message
news:zZoch.411882$R63.269149@pd7urf1no...


Just playing the devil's advocate for a moment...

Difficult to tell where any of us are in the world, so can't
even guess at where you might be, but those just about 1/2 voltages
might not be a coincidence...

It's not possible that you're in the UK and bought a North American
regulator, is it? :)


Sounds like a split 240 generator. Perhaps the regulator connections got
switched to the 240 leads instead of the 120 leads?





Wouldn't they only go to the 240 leads? If that output is correct, the
120 should be as well.

Generac 7500
 

"James Sweet" wrote in message
news:4Avch.3283$H22.203@trndny09...

Sounds like a split 240 generator. Perhaps the regulator connections got
switched to the 240 leads instead of the 120 leads?

Wouldn't they only go to the 240 leads? If that output is correct, the 120
should be as well.

You'd think but who knows? Without a circuit it's hard to diagnose.

Generac 7500
 

I have no experience with a generator of this size, so this may not be
relevant.

When my 2500-watt generator suddenly quit, I opened up the end bell and
found that there were a pair of stud-mounted power diodes inside. One
of the diodes had shorted, with the result that there was zero voltage
at the output. I'm not sure of the function of the diodes, but I think
they provided DC (unipolar) excitation to the field coils.

My generator was 120VAC only (no 240VAC). Perhaps yours has lost one
side of the 240VAC excitation, resulting in half voltage somehow.

Just FWIW.

Bill
--------------------------

James Sweet wrote:

Homer J Simpson wrote:

"Ken Weitzel" wrote in message
news:zZoch.411882$R63.269149@pd7urf1no...


Just playing the devil's advocate for a moment...

Difficult to tell where any of us are in the world, so can't
even guess at where you might be, but those just about 1/2 voltages
might not be a coincidence...

It's not possible that you're in the UK and bought a North American
regulator, is it? :)



Sounds like a split 240 generator. Perhaps the regulator connections
got switched to the 240 leads instead of the 120 leads?





Wouldn't they only go to the 240 leads? If that output is correct, the
120 should be as well.

Generac 7500
 

In article LBEch.15611$YV4.12081@edtnps89,
"Homer J Simpson" wrote:

You'd think but who knows? Without a circuit it's hard to diagnose.

Homer-

If you're interested, an owner's manual with a circuit that may be
similar to this one, can be found at
http://www.generac-portables.com/dat.../1019_1enw.pdf

The file is a little over a megabyte.

Fred

Generac 7500
 

Fred McKenzie wrote:
In article LBEch.15611$YV4.12081@edtnps89,
"Homer J Simpson" wrote:

You'd think but who knows? Without a circuit it's hard to diagnose.

Homer-

If you're interested, an owner's manual with a circuit that may be
similar to this one, can be found at
http://www.generac-portables.com/dat.../1019_1enw.pdf

The file is a little over a megabyte.

Fred
Thank you Fred. I have the parts and exploded diagrams for this unit.I
have schamatics for it also. The problem is I know just enough about
electricity to be dangerous. For instance the specs given for the
windings. I have an ohmmeter and can read it, I just don't know where
I'd attach it to get the readings. In the process of replacing the
voltage regulator I unscrewed the brushes assembly for access to attach
2 wires from the voltage regulator, and I think I seated the brushed
right. I will check this tomorrow, Monday. Thank you all.

Generac 7500
 

In article . com,
wrote:

...... I have an ohmmeter and can read it, I just don't know where
I'd attach it to get the readings. In the process of replacing the
voltage regulator I unscrewed the brushes assembly for access to attach
2 wires from the voltage regulator, and I think I seated the brushed
right. I will check this tomorrow, Monday. Thank you all.

One thing I forgot to mention, was that your symptoms might be caused by
having the Idle Control Switch turned ON. With no load, the engine goes
to a lower RPM, perhaps equivalent to 40 Hz, and voltage goes down
somewhat.

Do you have capability to measure frequency or RPM? The generator
probably runs at 3600 RPM to produce 60 Hz. (Some run at 1800, but I
don't think yours does.)

A problem measuring resistance of generator windings, is that the
resistance is so low that meter leads and their contact resistance can be
a higher value than the winding being measured!

The brushes ride on slip rings, which are connected to the rotating field
winding. You can measure field resistance by disconnecting the regulator
and measuring across the brushes. If resistance is too high, it could be
a problem with the brushes as well as the winding. With the brush
assembly unscrewed, you may be able to probe the slip rings directly.

The main winding connects via circuit breakers to the electrical outlets.
A 240 Volt outlet will have connections to the three main wires
(120-0-120). I don't know how much influence the breakers would have on
the measurements.

The excitation (DPE) winding connects to the regulator module as I recall.

Fred

Generac 7500
 

Bill Jeffrey wrote:
I have no experience with a generator of this size, so this may not be
relevant.

When my 2500-watt generator suddenly quit, I opened up the end bell and
found that there were a pair of stud-mounted power diodes inside. One
of the diodes had shorted, with the result that there was zero voltage
at the output. I'm not sure of the function of the diodes, but I think
they provided DC (unipolar) excitation to the field coils.

My generator was 120VAC only (no 240VAC). Perhaps yours has lost one
side of the 240VAC excitation, resulting in half voltage somehow.

Just FWIW.

Bill
--------------------------

James Sweet wrote:

Homer J Simpson wrote:

"Ken Weitzel" wrote in message
news:zZoch.411882$R63.269149@pd7urf1no...


Just playing the devil's advocate for a moment...

Difficult to tell where any of us are in the world, so can't
even guess at where you might be, but those just about 1/2 voltages
might not be a coincidence...

It's not possible that you're in the UK and bought a North American
regulator, is it? :)



Sounds like a split 240 generator. Perhaps the regulator connections
got switched to the 240 leads instead of the 120 leads?





Wouldn't they only go to the 240 leads? If that output is correct, the
120 should be as well.

Bill says maybe I lost half my excitation. That's exactly what I'm
thinking. Do I need to run the generator to flash the fields? I'm
thinking I disconnect the leads from the volage regulator @ the brushes
so I don't burn it out and take a 12v battery, connect the ground to
the chassis and the positive to one of the brushes for a second and
then do the other brush. If I understand what they are saying on
smokestak. Or maybe someone can walk me through flashing the fields so
both are remagnitized, and I'll run it for an hour to get the magnetism
to stay??

Generac 7500
 

wrote in message
ps.com...

Bill says maybe I lost half my excitation. That's exactly what I'm
thinking. Do I need to run the generator to flash the fields? I'm
thinking I disconnect the leads from the volage regulator @ the brushes
so I don't burn it out and take a 12v battery, connect the ground to
the chassis and the positive to one of the brushes for a second and
then do the other brush. If I understand what they are saying on
smokestak. Or maybe someone can walk me through flashing the fields so
both are remagnitized, and I'll run it for an hour to get the magnetism
to stay??

I would have great difficulty believing you need to flash any field magnet
these days - this isn't a Model A Ford. Look elsewhere.

Generac 7500
 

Generac 7500
 

In article om,
wrote:

Do I need to run the generator to flash the fields? I'm
thinking I disconnect the leads from the volage regulator @ the brushes
so I don't burn it out and take a 12v battery, connect the ground to
the chassis and the positive to one of the brushes for a second and
then do the other brush.

Ellombris-

NO. When the field needs to be flashed there is no output at all. If
there is ANY residual magnetism, there will be output, and almost
instantly it will build up to full value when you start the generator.

Something else is causing your problem.

Could it be the Idle Control switch is set to the "ON" position? That
would give your symptoms until you connect a load to the generator
output. If you connect a light bulb to the generator, does it light to
full brightness, or barely at all?

The diodes that rectify field current are in the module you replaced.
Unless it has an open diode, it is unlikely to be the problem.

When you installed the module, could you have connected the wires to the
brush assembly backwards? According to the Clymer manual, the White
wire connects to the positive brush, which is the one closest to the
bearing.

Fred

Generac 7500
 

Fred McKenzie wrote:
In article om,
wrote:

Do I need to run the generator to flash the fields? I'm
thinking I disconnect the leads from the volage regulator @ the brushes
so I don't burn it out and take a 12v battery, connect the ground to
the chassis and the positive to one of the brushes for a second and
then do the other brush.

Ellombris-

NO. When the field needs to be flashed there is no output at all. If
there is ANY residual magnetism, there will be output, and almost
instantly it will build up to full value when you start the generator.

Something else is causing your problem.

Could it be the Idle Control switch is set to the "ON" position? That
would give your symptoms until you connect a load to the generator
output. If you connect a light bulb to the generator, does it light to
full brightness, or barely at all?

The diodes that rectify field current are in the module you replaced.
Unless it has an open diode, it is unlikely to be the problem.

When you installed the module, could you have connected the wires to the
brush assembly backwards? According to the Clymer manual, the White
wire connects to the positive brush, which is the one closest to the
bearing.

Fred

I removed the brushes and seated them properly, it seems they were
already seated OK. Changed the wires to the brushes opposite to how
they were hooked up, got 0 voltage. Reversed them and I get 65vac @
the 120 outlets and 120vac @ the 240 outlet. There's nobody local, but
I'm gonna try the closest to me, about 50 miles away that supposedly
works on generators. Otherwise this unit will be on sale on E-bay as is
to the highest bidder.

Generac 7500
 

Generac 7500
 

In article . com,
wrote:

I removed the brushes and seated them properly, it seems they were
already seated OK. Changed the wires to the brushes opposite to how
they were hooked up, got 0 voltage. Reversed them and I get 65vac @
the 120 outlets and 120vac @ the 240 outlet. There's nobody local, but
I'm gonna try the closest to me, about 50 miles away that supposedly
works on generators. Otherwise this unit will be on sale on E-bay as is
to the highest bidder.

Ellombris-

It can be frustrating. If the System Control Board (where voltage is
adjusted) happens to be bad, they cost around $200 to replace. Unless
you had one to try, you can't be sure the old one is bad!

You might measure the DC voltage across the brushes when it is putting
out 65 VAC, to get an idea how it is performing. You might also
reconnect the brushes to an external DC power supply, and see what
voltage it takes to get the proper output.

Of course this information would only be of value if you knew what to
compare it with, but you could verify that the alternator is capable of
putting out full voltage.

Applying a load and measuring voltage change would give you an idea of
regulation. If it falls from half value to zero, the problem is worse
than if it only drops ten percent!

Fred