Hi Folks! I'm a brand new member (and newbie welder too), with a broken MM 135 (Serial #LB265626; board # 199820). I've been reading through the amazing wealth of troubleshooting info you've all provided, but I've yet to fix my issue.
Short version: Wire isn't feeding. The motor won't turn, even without wire. Gun (or shorting gun connection) just generates a clicking relay (my troubleshooting attempts listed below). Motor does run with 12v power.
Long version: This unit was purchased used. Seller demoed it for me, then it sat for about a year in my garage before I got up the courage to mess with it. The machine was exactly how the previous owner had left it -- .23 wire, 75/25 gas, feed tension at 3.
It worked great for about 30 minutes (maybe 3-4 minutes of actual welding/bead time, though not continuous). After a bit of hunting around for some more scrap, I was ready to go again. At some point in there, I knocked the gun off my table and onto the ground. That maybe just coincidence, but the machine wouldn't feed wire when I started up again. (trigger causes click, but no motor action). I'm thinking I maybe damaged the tip and that jammed the feed and "tripped" some sort of protection (or burned some sort of circuit). But that's just a theory based on what I've read in a ton of 135/175 threads. Most of these are related to erratic wire speed issues versus my "no feed" situation, but hey, gotta start somewhere!
Here's what I've checked so far:
- Removed all tension from wire/gun leaving a naked feed wheel. Fed wire both ways through gun to check for kinking or blocked liner.
- Unplugged the unit and let it rest, thinking this would allow a thermal breaker to reset. However even without wire the trigger only generates clicks from relay (but doesn't spin motor).
- Removed gun from trigger recepticle. Shorted pins there. Behavior is just like gun trigger (clicks but no motor action).
- Checked power at terminals above wire feed mechanism. I set voltage at 5 and see 23 volts DC at terminals.
- Opened case. Red light comes on with clicking. Checked circuit board for good connections. Looked for obvious burning, bloating, etc. None found.
- Unplugged motor pigtail. Applied 12v battery power to motor side of connector. Motor (and gearing) spin fine.
- Checked continuity of PTC1. Closed. Jumpered (as best as I good -- this seems kinda iffy to get in there safely and effectively) and got same clicking result.
- Checked legs of Q1, Q4, Q8. No continutity between legs -- I *think* that is something I'm supposed to be checking .
- Q5 seems to get the most attention as problematic on the 135/175, but on this board, Q5 is a really tiny 1/2 round unit -- no heat sink like I've seen in most of the other thread.
Next step?: I guess I'll try to re-flow the solder for PTC1. I'm thinking a brittle joint could be causing it to act open. And maybe I'll order one and replace it for the heck of it.
But that's all I can come up with. The board is on my desk now. I'm happy to take measurements (I have an autoranging dmm, but no clamp for amperage -- I'll buy one though if that helps!), if anyone can point me in the right direction.
Thanks in advance for any help you can throw my way!
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01-22-2014, 03:09 PM #1Junior Member
- Join Date
- Jan 2014
MM 135 no wire feed, no motor action. Clicks only