Help with SP125 Plus Feed

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This is my 1st post and sure not the last. I pick up a used SP125 Plus used at what I thought was a good price but found that the wire feed had only one speed when turning the speed dial and may not be getting hot as I feel it should. I have check the liner and wire spool, also do not see any loose connection inside or any burn marks on the board. I live in the rural and no repair shops near. So could sure use some help with this problem. I was told the machine had sit for awhile unused and I can not see any abuse to the unit. I hope this to be an common problem and ease fix, But I know better.Thanks in advance
Reply:Welcome to the forum. I’m not familiar with that unit and not a technician so unable to help but adding posts may attract attention of the guys who do repairs. Good luck on getting it going.Burt _____________________Miller Syncrowave 250Millermatic 211Miller 375 Plasma Cutter Hobart Handler 12010FtDrillBit.com
Reply:Thanks WB for I sure can use the help.
Reply:

Originally Posted by rab

This is my 1st post and sure not the last. I pick up a used SP125 Plus used at what I thought was a good price but found that the wire feed had only one speed when turning the speed dial and may not be getting hot as I feel it should. I have check the liner and wire spool, also do not see any loose connection inside or any burn marks on the board. I live in the rural and no repair shops near. So could sure use some help with this problem. I was told the machine had sit for awhile unused and I can not see any abuse to the unit. I hope this to be an common problem and ease fix, But I know better.Thanks in advance
Reply:i still have my sp125 i bought new.  have run probably run 50-75 2lb spools thru mine.  great machine  like rondo said as you turn the wire speed up the motor noise and speed does increase.  i will look today and see if i still have the manual with mine.  if so i will reply back with wiring diagram.    do you have the manual or does anyone know if it is download from lincoln?lincoln 125spmonkey wards 250 ac/dcmiller 211 w/spool gunahp  200 sx tiglotos ltp5000dof course duramax diesel
Reply:Thanks rob, I do not have a manual, but was looking on line at a user manual for trouble shooting and it was of no help for this problem. I do not hear any change in the motor loudness when dialing the pot, But I don't hear the good at 77.
Reply:if you open the door that the wire goes in where the drive rollers are, the drive roller can be seen changing speeds as u move dial.  might have to open it up and look at back of switch.  i don't know, but maybe spray electrical contact cleaner might work.  this is out of my expertise.lincoln 125spmonkey wards 250 ac/dcmiller 211 w/spool gunahp  200 sx tiglotos ltp5000dof course duramax diesel
Reply:The potentiometer could be bad or the inside of it dirty. If you have an ohmeter, you could disconnect the wires, then test it with the meter to see if the resistance changes
Reply:A1 would you by chance know the values that I would be getting if the pot is working correct? Or anyone that may know.
Reply:Not sure on yours but mine varies from ~ 400 Ohms to 5K ohmsLincoln Idealarc Tig 250, Airco Dipstick 160, Lincoln Square wave Tig 175
Reply:A1 ,Thanks for the information.
Reply:Connect a voltmeter and read the voltage on the large capacitor at the front of the welder. should be 0 vdc until you pull the trigger. Should increase and decrease with turning of the weld voltage control. We have to have good weld voltage before we can have wire drive. Should be a wiring diagram pasted inside the cover.Voltage should be 28vdc with voltage control all the way up. This is the no load voltage. This is fed into the pcb and back out to the motor. Try putting a volt meter across the speed control. out side terminals. guessing it should be around 10vdc.might have to pull gun trigger for voltage to get there. Out side terminal to center will vary from 0 to "10" volts. Before you take cover off, release pressure arm on the drive so wire will not feed. Now pull trigger and run speed for min to max. Watch drive roll, you should be able to see and hear it speed up. Now if it is stuck at one speed the question is low or high speed. High speed with no control is a shorted drive transistor. If you cant tell the speed. lock pressure arm down a feed 6 seconds of wire. Measure wire and times it by 10. 20 inches of wire by 6 seconds = 200ipm.Max wire speed should 400 to 500 ipm.