mm175 drive motor problems

[lopez62566]

I have mm175 have feed motor problem i got voltage on connector to dm but i think no amps to push the volts any boby with ideas on what to check on board. Got gas,arc just no feed
serial-le187988
stock-907020
board#207466
new drive motor:rolleyes:

[cruizer]

Unlikely to be a wirespeed control potentiometer as you'd still have limited wire speed, all your left with is the drive itself (possibly a thermal trip from over tightening the drive rolls) or the control board

To test the motor (disconnect the motor leads) with the wire speed knob at
zero shere should be 1 volt, at max 20.5 volts DC. If the voltage is there, the board is good, and the motor is bad, if its not there then the board is bad, and the motor is probably good

[lopez62566]

Yes, i got voltage from the board to the motor 1 volt lowest setting and 20 volt highest.Thats why i got a new motor drive assy the gear box and motor and still same problem. i can take the motor and hook it up to a power supply and its fine or i can take a regular 12volt light bulb and hook it up to the out put of the board of the welder an make the light dim out or bright with the wire speed knob . any ideas

[cruizer]

With the leads off the "New" motor what is your resistance reading on the motor , should be less than 2 ohms

As usual I read the Voltage values wrong.

With the voltage and wire speed knobs at min there should be 1 Vdc at the motor

With both the voltage and wirespeed knobs at max there should be 20.5 Vdc at the motor

[lopez62566]

Ok ohms across motor 2.2 ohm.Another thing that got me wondering is with the the volt meter across the motor leads with the connector plug to the board an hit the trigger ,voltage is .341 on the meter and un connected is regular volts 1 to 20 volt by turning the wire speed up and down. Do you know which curcuit on the board controls this or diode,resistor to check

[cruizer]

Tryed to down load the service manual, but my computer is not being too eager to do that for me this morning, sooooo, the diode your after is D3, however according to the diagram, at idle or off it'll be shorted through a control relay, so you won't get a definative reading off RC3-5, & RC3-6 which leads to the motor.

That whole board lists out at $300

[lopez62566]

I will check the D3 diode is there any way you can send me the diagram on the board.Do you think replacing the board is my only option i like the messing around with this stuff.

Thanks for all the info on this machine

[lopez62566]

OK D3 diode checks out to be good ,what relay is the control relay there are three relays same part # first two from left to right are warm the other one is cold is this the one ?

Thanks

[cruizer]

OK D3 diode checks out to be good ,what relay is the control relay there are three relays same part # first two from left to right are warm the other one is cold is this the one ?

Thanks

Errr, how did you check it? you'd have to pull it from the circuit to test or have a tracker, besides the whole thing doesn't make sence as you have power off the board to run the motor

If it was me I'd be inclined to take it to a service depot, instead of chasing ghosts.

What was the # for that motor you ordered?

[lopez62566]

Yes Sir took the diode out of board and check it resistance one way not the other.The motor i got for this machine is part# 202708 and the board # is 207466 is there any thing else to check ive got voltage just drops when motor is pluged in.

[cruizer]

Did you happen to try the motor out of the drive housing with the board.

[lopez62566]

Yes Sir, inside the machine and outside the machine.I got another dc motor from a drill i belive checked the ohms 1.2 and its a 9volt motor wired it to the leads on the board and it does fine low rpm not full speed i can speed it up or lower the speed with wire feed knob.

[cruizer]

Well all you can look at now is RC4-3, and RC3-4 with the machine on to check for DC output voltage. If that is there then yep your board is hooped.

I'd guess that CR1 is not operating, guarenteed it's going to be a relay but which one....

[lopez62566]

I found RC3-4 could not find RC4-3 so i checked RC3-4 and RC3-3 just to see what it was and it is 20.16 volts dc with the trigger pushed these go to the capacitor is this were the motor gets it voltage.Any idea were on the board is this RC4-3 ,i see were i can get the relays and change all three if i have to i think its that cr3 cause it cool the others are warm and the two heat sink are cold its like that side of the board is not working.

[cruizer]

Sorry that was a mis write, should have said RC3-3 and RC3-4. As for the relays, you can carefully cut the tops off them to see if they are working, really you have nothing to loose at this point other than replacing the board.

[lopez62566]

Ok,I will let you know how it goes

[lopez62566]

OK cut the top of the three relays all close and open but on cr1 getting resistance from the the normaly open leg to the coil ? I will mess with it some more today ,maybe pull it from the board

[cruizer]

OK cut the top of the three relays all close and open but on cr1 getting resistance from the the normaly open leg to the coil ? I will mess with it some more today ,maybe pull it from the board

By the looks of the diagram, CR-1 looks to be on a delay

[lopez62566]

That might be the resistance i am getting then

[lopez62566]

I need some input on D2 whats the deal regular diode or special part shows its bad and did some searching and maybe fails under a load ,what do you think.