MIG wire speed control problems

[Rafael Ramos]

Hi all:

I am trying to repair the wire speed control on a Century welder Model
83132. The control has a very short usable range and past position 4 is
faster than 700 IPM, so it is almost impossible to "tune it in". Is there a
place where I can buy a pc board for this unit or get a schematic of the pc
board with the parts values. I don't think the Century factory keeps parts
for these old machines. Who owns Century now? I called the support
number and somebody from Lincoln answered. BTW, I know that I am going to
get the advice to throw the Century away and get a Red or Blue machine.
Well, I am seriously considering buying the Millermatic 210 or a similar
machine. Any suggestions?

Thanks for your response

Best Regards,

Ray Ramos

[John Crighton]

On Mon, 15 May 2006 03:16:07 GMT, "Rafael Ramos"

Post by Rafael Ramos
I am trying to repair the wire speed control on a Century welder Model
83132. The control has a very short usable range and past position 4 is
faster than 700 IPM, so it is almost impossible to "tune it in". Is there a
place where I can buy a pc board for this unit or get a schematic of the pc
board with the parts values. I don't think the Century factory keeps parts
for these old machines. Who owns Century now? I called the support
number and somebody from Lincoln answered. BTW, I know that I am going to
get the advice to throw the Century away and get a Red or Blue machine.
Well, I am seriously considering buying the Millermatic 210 or a similar
machine. Any suggestions?
Thanks for your response
Best Regards,
Ray Ramos

Hello Ray,
Have you checked the potentiometer that controls the motor speed?
Maybe it is dirty.
Unsolder the wires to the potentiometer and use a multimeter on the
ohms range to check that the wiper contact of the potentiometer
changes resistance smoothly when the shaft is turned smoothly,
measuring between wiper and either end of pot. with the ohmmeter.
An analog meter with needle pointer is best for this test.

Look for loose and dirty connectors on the motor control board.
Tighten up/clean any connections that look dodgy.

Obtaining a schematic would be ideal, then repair would
be easy but don't give up on that idea yet, keep looking.
In the mean time you could isolate the two motor connections
and build your own speed control in a separate box for less
than $20 in parts.

Google
motor speed control
There are lots of schematics to choose from.

Here is the third hit down
http://www.solorb.com/elect/solarcirc/pwm1/
Here are details of a kit.
http://www.ozitronics.com/docs/k67v3.pdf

I prefer the first link above because it is important
to find a good quality wire wound potentiometer.
The ohmic value of potentiometer VR1 is not critical
in the solor circuit above.
You can find a good quality wire wound pot. in your
junk box (or friends junk box) or from junked equipment
and use it.
Any value between 1000 ohms and 10,000 ohms will
be fine. You just have to reduce the values of R6 and R7
accordingly. Better still, make R6 and R7 trimpots.
Having found a good quality pot for free, the rest of
the components are peanuts in dollar value.

Once you have built a speed controller and got
your welder functioning again you can take your
time finding the Century schematic and repairing
the faulty Century board.
Just a suggestion.

Regards,
John Crighton
Sydney



*** Posted via a free Usenet account from http://www.teranews.com ***

[Rafael Ramos]

Thanks John, Now I have done some of what you mention and everything seems
to work ok, the pot is nice and smooth (with analog voltmeter) and the board
checks out OK. There is a nice big elecrtrolitic capacitor filtering the 24
volts that looked bad, the positive side looked black and some sort of film
on the outside, I unsoldered it and measured and it was OK too. I am
certain that the problem is in the wire feed mechanism. There is only one
active wheel that is pushing the wire and I think it is encountering
changing pressure from the wire spool when trying to spool the wire out.

I am now looking at better and more powerful mig machines and plan to
purchase a new welder in the very near future. The old Century will be
relegated to an experimental machine that I plan to modify and learn details
of the mig welding circuitry.

Thanks again for your very informative reply. I plan to use the information
to start my files on how to do the modifications.

Best Regards,

Ray

Post by John Crighton
On Mon, 15 May 2006 03:16:07 GMT, "Rafael Ramos"

Post by Rafael Ramos
I am trying to repair the wire speed control on a Century welder Model
83132. The control has a very short usable range and past position 4 is
faster than 700 IPM, so it is almost impossible to "tune it in". Is there a
place where I can buy a pc board for this unit or get a schematic of the pc
board with the parts values. I don't think the Century factory keeps parts
for these old machines. Who owns Century now? I called the support
number and somebody from Lincoln answered. BTW, I know that I am going to
get the advice to throw the Century away and get a Red or Blue machine.
Well, I am seriously considering buying the Millermatic 210 or a similar
machine. Any suggestions?
Thanks for your response
Best Regards,
Ray Ramos

Hello Ray,
Have you checked the potentiometer that controls the motor speed?
Maybe it is dirty.
Unsolder the wires to the potentiometer and use a multimeter on the
ohms range to check that the wiper contact of the potentiometer
changes resistance smoothly when the shaft is turned smoothly,
measuring between wiper and either end of pot. with the ohmmeter.
An analog meter with needle pointer is best for this test.
Look for loose and dirty connectors on the motor control board.
Tighten up/clean any connections that look dodgy.
Obtaining a schematic would be ideal, then repair would
be easy but don't give up on that idea yet, keep looking.
In the mean time you could isolate the two motor connections
and build your own speed control in a separate box for less
than $20 in parts.
Google
motor speed control
There are lots of schematics to choose from.
Here is the third hit down
http://www.solorb.com/elect/solarcirc/pwm1/
Here are details of a kit.
http://www.ozitronics.com/docs/k67v3.pdf
I prefer the first link above because it is important
to find a good quality wire wound potentiometer.
The ohmic value of potentiometer VR1 is not critical
in the solor circuit above.
You can find a good quality wire wound pot. in your
junk box (or friends junk box) or from junked equipment
and use it.
Any value between 1000 ohms and 10,000 ohms will
be fine. You just have to reduce the values of R6 and R7
accordingly. Better still, make R6 and R7 trimpots.
Having found a good quality pot for free, the rest of
the components are peanuts in dollar value.
Once you have built a speed controller and got
your welder functioning again you can take your
time finding the Century schematic and repairing
the faulty Century board.
Just a suggestion.
Regards,
John Crighton
Sydney
*** Posted via a free Usenet account from http://www.teranews.com ***

[Gunner]

On Fri, 26 May 2006 02:11:14 GMT, "Rafael Ramos"

Post by Rafael Ramos
Thanks John, Now I have done some of what you mention and everything seems
to work ok, the pot is nice and smooth (with analog voltmeter) and the board
checks out OK. There is a nice big elecrtrolitic capacitor filtering the 24
volts that looked bad, the positive side looked black and some sort of film
on the outside, I unsoldered it and measured and it was OK too. I am
certain that the problem is in the wire feed mechanism. There is only one
active wheel that is pushing the wire and I think it is encountering
changing pressure from the wire spool when trying to spool the wire out.

Ive been having a somewhat similar problem with my old Dan-Mig 200.

Wire has been hit and miss..get a good arc going..and it would spit
and sputter. <snip a lot of trouble shooting> and it turned out to be
an old and tired liner.. Id been given some liners that were the right
length and ID..but the fitting on the end was too big.

I stuck the liner in the lathe, ran the length into the bar feed tube
and turned it down to the proper dimensions. Old bitch runs good
again. I can now put a fairly sharp bend in the gun cable and it will
still feed just hunky.

Gunner


"The importance of morality is that people behave themselves even if
nobody's watching. There are not enough cops and laws to replace
personal morality as a means to produce a civilized society. Indeed,
the police and criminal justice system are the last desperate line of
defense for a civilized society. Unfortunately, too many of us see
police, laws and the criminal justice system as society's first line
of defense." --Walter Williams

[Rafael Ramos]

Hi Gunner:

Thanks for your reply. You brought out a good point that I had not
considered, and could very well be the culprit. I will check the liner and
the rest of the gun past the driving wheel and make sure there are no
obstructions and the wire has a free flow through it. I guess a liner is
available and probably not too expensive so I will order one Monday just in
case. I'll let the group know the results. Lincoln is now the owner of
Century welders and they have most of the parts available for this welder .
I am now at a point in my mig welding that I am seriously considering an
upgrade to the big players, I am looking at the Miller 251 and the Lincoln
255. Yesterday I stopped at Intermountain Airgas and General Air and looked
at their machines. If I solve the problem with the Century I will not have
an excuse to spend all that money for a new welder, but it would be great to
solve the mystery, and I can always find another excuse for the purchase.
Thanks again for your advice.

BTW, I enjoy reading your postscripts.

Best Regards,

Ray R

Post by Gunner
On Fri, 26 May 2006 02:11:14 GMT, "Rafael Ramos"

Post by Rafael Ramos
Thanks John, Now I have done some of what you mention and everything seems
to work ok, the pot is nice and smooth (with analog voltmeter) and the board
checks out OK. There is a nice big elecrtrolitic capacitor filtering the 24
volts that looked bad, the positive side looked black and some sort of film
on the outside, I unsoldered it and measured and it was OK too. I am
certain that the problem is in the wire feed mechanism. There is only one
active wheel that is pushing the wire and I think it is encountering
changing pressure from the wire spool when trying to spool the wire out.

Ive been having a somewhat similar problem with my old Dan-Mig 200.
Wire has been hit and miss..get a good arc going..and it would spit
and sputter. <snip a lot of trouble shooting> and it turned out to be
an old and tired liner.. Id been given some liners that were the right
length and ID..but the fitting on the end was too big.
I stuck the liner in the lathe, ran the length into the bar feed tube
and turned it down to the proper dimensions. Old bitch runs good
again. I can now put a fairly sharp bend in the gun cable and it will
still feed just hunky.
Gunner
"The importance of morality is that people behave themselves even if
nobody's watching. There are not enough cops and laws to replace
personal morality as a means to produce a civilized society. Indeed,
the police and criminal justice system are the last desperate line of
defense for a civilized society. Unfortunately, too many of us see
police, laws and the criminal justice system as society's first line
of defense." --Walter Williams

[Thesykboy]

Hey gang, I read this thread in hopes of finding the cure to my issue (which is similar). Got a Craftsman (Century) from 1992. First time in years I’ve used it and I’ve noticed the wire feed is slow AND weak. I can literally stop the wire feed roller with my fingers (and reasonable pressure) on full speed. I’ve replace the gun, liner, and everything recently because the old one was just too stiff. I also did so in hopes it would solve the feed issue… nope.

I’ve tested the motor on a 12v battery directly and can see that it and the gearbox are working fine - torque and speed. It was hauling ass and I couldn’t stop it with the same pressure as before. I spoke to someone at Lincoln (who now owns Century) and was told the board is likely not putting out the amps the motor needs for proper torque. I just bought the board, but don’t want to throw parts at it. I know something isn’t putting out the right amount of juice and I’m trying to figure out where it’s NOT coming from. Does this make sense to anyone else? I know things get old and stop working, but like the others, I’m not familiar with circuitry and and reluctant to just throw parts at it. I love this welder and really want it to work.

Thanks in advance for the knowledge.

-Jason from Denver.

[Jim Wilkins]

"Thesykboy" wrote in message news:175ed073079f0ac8$36$565070$***@news.newsgroupdirect.com...

Hey gang, I read this thread in hopes of finding the cure to my issue
(which is similar). Got a Craftsman (Century) from 1992. First time in years
I’ve used it and I’ve noticed the wire feed is slow AND weak. I can
literally stop the wire feed roller with my fingers (and reasonable
pressure) on full speed. I’ve replace the gun, liner, and everything
recently because the old one was just too stiff. I also did so in hopes it
would solve the feed issue… nope.

I’ve tested the motor on a 12v battery directly and can see that it and
the gearbox are working fine - torque and speed. It was hauling ass and I
couldn’t stop it with the same pressure as before. I spoke to someone at
Lincoln (who now owns Century) and was told the board is likely not putting
out the amps the motor needs for proper torque. I just bought the board, but
don’t want to throw parts at it. I know something isn’t putting out the
right amount of juice and I’m trying to figure out where it’s NOT coming
from. Does this make sense to anyone else? I know things get old and stop
working, but like the others, I’m not familiar with circuitry and and
reluctant to just throw parts at it. I love this welder and really want it
to work.

Thanks in advance for the knowledge.

-Jason from Denver.

---------------------

Posted to sci.engr.joining.welding

The schematic for a Century Powermate 70 shows two apparently selenium
rectifiers, a speed control pot and the torch switch in the wire feed motor
drive. Any of them could be the problem.
-jsw

[Richard Smith]

Post by Thesykboy
Hey gang, I read this thread in hopes of finding the cure to my issue
(which is similar). Got a Craftsman (Century) from 1992. First time in
years I’ve used it and I’ve noticed the wire feed is slow AND
weak. I can literally stop the wire feed roller with my fingers (and
reasonable pressure) on full speed. I’ve replace the gun, liner, and
everything recently because the old one was just too stiff. I also did
so in hopes it would solve the feed issue… nope.
I’ve tested the motor on a 12v battery directly and can see that it
and the gearbox are working fine - torque and speed. It was hauling
ass and I couldn’t stop it with the same pressure as before. I spoke
to someone at Lincoln (who now owns Century) and was told the board is
likely not putting out the amps the motor needs for proper torque. I
just bought the board, but don’t want to throw parts at it. I know
something isn’t putting out the right amount of juice and I’m
trying to figure out where it’s NOT coming from. Does this make
sense to anyone else? I know things get old and stop working, but like
the others, I’m not familiar with circuitry and and reluctant to
just throw parts at it. I love this welder and really want it to work.
Thanks in advance for the knowledge.
-Jason from Denver.
---------------------
Posted to sci.engr.joining.welding
The schematic for a Century Powermate 70 shows two apparently selenium
rectifiers, a speed control pot and the torch switch in the wire feed
motor drive. Any of them could be the problem.
-jsw

A wider overall point:

With a MIG / GMAW welder, you deliberately set the drive rolls so they
will skid if the wire jams.
You set the pressure so the wire will feed, but any more resistance
than regular feed and the rolls slip on the wire.
That's the reason for the springs on the toggles mechanism for the
drive rolls.

[Thesykboy]

The problem is, there doesn’t seem to be enough amps to the feed motor to power it with the torque it needs to move the wire. I’ve run the wire through 2 different liners and the resistance in the feed is the same. So I’m guessing the motor has to have a bit of torque to feed the wire.

Last night I tested amps where the leads come from the board to the motor. When the pot is set at 2, it reads .26 amps. When I keep cranking it up to 6, it hits .30 amps, and at 8…. same .30 amps. I’ve looked at other motors online to get a baseline of how many amps that motor should need to do its job. Even the cheap ones on Amazon are doing .90, so I’m thinking the amps coming from the board are way too low. I found a company that sells a new OE board with pot and voltage dials on it for a decent price. I don’t want to just throw parts at it, but in my research so far, everything points to what is sending amps the the motor… the board.

Sound about right

[Jim Wilkins]

"Thesykboy" wrote in message news:175f24e35dcf3418$1$3685597$***@news.newsgroupdirect.com...

The problem is, there doesn’t seem to be enough amps to the feed motor to
power it with the torque it needs to move the wire. I’ve run the wire
through 2 different liners and the resistance in the feed is the same. So
I’m guessing the motor has to have a bit of torque to feed the wire.

Last night I tested amps where the leads come from the board to the motor.
When the pot is set at 2, it reads .26 amps. When I keep cranking it up to
6, it hits .30 amps, and at 8…. same .30 amps. I’ve looked at other
motors online to get a baseline of how many amps that motor should need to
do its job. Even the cheap ones on Amazon are doing .90, so I’m thinking
the amps coming from the board are way too low. I found a company that sells
a new OE board with pot and voltage dials on it for a decent price. I
don’t want to just throw parts at it, but in my research so far,
everything points to what is sending amps the the motor… the board.

Sound about right?

------------------------------

A partly open bridge rectifier diode will give you the no-load voltage but
not the full current. Half-wave rectification is obvious if you have an
oscilloscope. It might show up as a large voltage difference between when
the motor is connected and disconnected.

If you can find an electrical schematic for it I might be able to suggest
other tests to locate the fault.