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Millermatic 175 = NO Feed Roller Movement

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25K views 38 replies 9 participants last post by  Bonzoo  
H
#1 ·
Long time Lurker, 1st time Poster.. I recently picked up a Millermatic 175 2nd hand and Knew going into the transaction that there was Feed Issues. I bought it worth the Money ( I think? $170) and finally got around to inspecting my purchase today. I decided to Run the Welder Dry with NO Wire to see if the Feed roller would spin, Negative.. I have Zero action when the Trigger is Engaged, I do have Relay Noises coming from inside the Machine but No Roller spin. I decided to remove the small Feed Roller Panel and see if i had any loose Connections at the Motor, Everything looked good as they were soldered. Here is my Plan of Attack.

1. Check to see if im getting Power at the Feed Motor assembly when the Trigger is engaged.

a. If i have Power, Tear into the Motor/Roller assembly looking for Problems

b. If No power, Tear farther into the Machine to see if there are connection issues between the Motor and the Circuit Board.

Obviously.. Im No Authorized Service Center, And i have no issue putting some money into the Unit, but i dont want to get near a New Machine Price Wise.

Is there something that im Missing? I apreciate Any and All Suggestions.

Thanks, Steven
 
H
#4 ·
Congrats on Improving your Welder with some Innovative work. I guess im not following how your Problem relates to mine, With exception that i Might have a Loose/Bad connection from the Board to the Motor. It appears that you had some Intermittent Load issues while welding and Mine has Zero Voltage at the Motor while engaging the Trigger. I scanned the Electrical Schematics from Millers site but its hard to see on the Computer.

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C
#8 ·
Look on the pcb. Find RC3 pin 3 Find the PTC1 between pin 3 and Diode D6.
Should be very low ohms between D6 cathode (stripe) and pin 3.
The PIC1 act like a resetable fuse to high motor current. Caused by a bad liner in the miggun. If worked to hard they open up and stay open. Just replace it or the complete pcb. MAKE SURE WELDER IS UNPLUGGED WHEN COVER IS OFF FOR TESTING.
 
D
#13 · (Edited)
Set your meter for DC volts. Set the voltage dial to 5. Power the unit up. With the gun trigger depressed check to see if you have around a 23- 25 open circuit voltage reading at the +/- output studs in the wire drive compartment.

You more than likely either have a relay issue or a failed transistor. I know which transistor was troublesome on the Hobart 135/175 but off the top of my head I don't remember which one it is on the Millermatic 135/175.
 
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H
#14 ·
Thanks Dan, I will check the voltage tomorrow and Report back. As i stated earlier i replaced the PTC1 (Bigger one) today and it didnt remedy the Sitsuation. In the Picture below (circled in Red) it looks like there might be another Thermal in the Lower Right hand corner. I hooked the Ohm meter up to the little disc and it showed .002 Resistance at the 2k setting where its Zero on the Bigger one. I think i said earlier that im not Electronic Guru, I run Freight trains and Rebuild Hydraulic Jacks. Any help is Surely apreciated..

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H
#20 ·
Well.. Im not sure if there is 4 of them or 3, If you look in the Lower Right corner of picture 4 above you will see what appears to maybe be a 4th, The Heat sink isnt near as big as the other 3 but it does have a "C" heat sink around it and there is Resistance between the bottom 2 prongs.
 
D
#22 ·
Before you worry about anymore circuit board components, do the test for voltage at the output power studs. Due to the design of the unit, if you don't have weld output power you aren't going to have power to the feed motor.
 
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H
#24 ·
While i got you guys here, Is this machine worth putting a New/Repaired Board into? So Far i have $170 bucks into the Machine. When i bought it, The Polarity was set up for Flux Core Wire and the Previous owner (Pawn shop) had Regular Mig Wire in it. Worst Case Scenario.. Outside of a Rebuilt/New Board is there other things that can cause problems down the Road? I had intentsion of Replaceing the Liner to prevent any Overheating issues caused by funky liner/bent/Rust etc..
 
D
#25 ·
I am not a fan of the MM 175. The wire speed tracking circuitry Miller used on the unit makes it a little finnicky to dial the arc in. The way the unit is design if you make an adjustment to the voltage dial, it changes the rate at which wire is being feed for the same wire speed dial setting. So, in most cases, a slight adjustment of the voltage dial also required you to make an adjustment to the wire speed dial.


The MM 175 is also weak in the area of arc starts. Miller corrected this issue on the MM 180 with run-in circuitry. Shortening up the length of of the spool hub tensioning spring on the unit I use to own helped improve the quality of the arc starts. You still had to make certain to trim the wire everytime and keeping a short stick out length of 1/4" - 3/8" helped too.
 
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D
#28 ·
Dan said, "I am not a fan of the MM 175. The wire speed tracking circuitry Miller used on the unit makes it a little finnicky to dial the arc in. The way the unit is design if you make an adjustment to the voltage dial, it changes the rate at which wire is being feed for the same wire speed dial setting. So, in most cases, a slight adjustment of the voltage dial also required you to make an adjustment to the wire speed dial.

The MM 175 is also weak in the area of arc starts. Miller corrected this issue on the MM 180 with run-in circuitry. Shortening up the length of of the spool hub tensioning spring on the unit I use to own helped improve the quality of the arc starts. You still had to make certain to trim the wire everytime and keeping a short stick out length of 1/4" - 3/8" helped too."

My question was going to be about MM 175 Arc Starts.
After reading Dan's reply, can I replace the 175 board with a 180 board the has this "run-in" circuitry?
 
M
#29 ·
Hi All,
I'd like to resurrect this thread if I can; as my Millermatic 175 has developed the same problem. I've been digging around the intertubes looking for a similar discussion for this problem and you guys seem to know the most about it. the circuit diagram in my owners manual doesn't show the same circuit nomenclatures as what has been called out in this thread by CCAWGC. is there a different circuit diagram I should be looking at? my serial number is: LC524536.
thanks in advance for the help!
regards
Mark
 
C
#30 ·
That is why we ask over and over for serial number when giving help. Things change over time and some service manuals can have up to 10 or more diagrams. The best diagram for your machine should be the one pasted inside the cover.
Start by seeing if you have Voltage at the weld terminals Next to the drive motor. When you pull the gun trigger.
If you have voltage you then can unplug the welder and remove the cover. Find the motor plug and using a 6 or 12 volt battery connect it to the motor. ( unplugged form harness) If motor runs. there is a problem in the wiring or the pcb.
Weld voltage has to return to the pcb so it can be used as a power source for the motor drive control.
 
M
#31 ·
Thanks for replying! I messed around with the machine a bit and realized it does feed wire.....only when the voltage is turned up past 20 and then the wire feeds at full speed only. It still welds great as long as you're welding 1/4" material!
I did some more digging around and found a couple references to the problem lying in the Darlington pair transistor that apparently controls wire speed. The thread I found even gave the ordering info to replace the transistor but no picture of where it is on the board. It's one of the three mounted to the three heat sinks on the board but which? Would you have some clarification in that? Even the alpha numerical number of the component on the board would be great!
Thanks again
Mark
 
D
#37 ·
Update on an OLD Thread!
Its again April(4th month) but a year later!
LOL!
After the MM175 sat on the shelf for a year, I got around to it on Easter day! When I first turned it on, it fed wire freely, I ran some beads at 3 different settings (3, 6, 9). As it warmed up the wire feed motor ran slower and slower until depressing the trigger gave about 4 inches with decaying motor speed till the wire stopped coming out. It almost sounds like Q5 is bad as it warms up?
I really need to get this thing fixed this year.........
 
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