Hi Doug.
Not familiar with that machine, but I would check the simple things first.
1. Good ground, ground clamp lead tight at both ends.
2. MIG gun fully seated - it will disengage slightly if pulled by gun and hard to be sure fully seated. Loosen, remove, re-insert and tighten.
3. Power lead snug to the stud.

Good luck. It is more likely something simple.

 

Hey Burt,
Thanks for the suggestions. This Millermatic was gone through about 3 years ago, all female (yellow) connectors were replaced and it had a brand new M25 gun on it. I feel that all external connections are good.

The contactor is probably shot Doug. Pretty common on these types of machines. When the contacts get worn, power cannot fully transfer through it. As power is transferring thru the contacts, the lack of good connection is what causes the buzzing. Sometimes other components inside them come loose and cause excessive noise, but most of the time poor output and loud noise coming from the machine is a classic case of contactor failure/need of service.

I believe it's a two pole, 30 or 40 amp job, with a 24 VAC coil. You can buy a replacement almost anywhere online. I buy them from an HVAC company on eBay for the Maxtrons and they're under $20/ea. You don't need to buy an expensive one IIRC, it's a two pole job, but even a three pole one would work. As long as the configuration is similar and coil voltage is the same, you're good to go.

That's almost a certainty what the issue is. You can even take it apart and dress the contact points to get you by for the time being. It's the component that looks like a big open relay with larger wires running to and from it. And as Burt said, check the pin connections and make sure they're not heavily pitted or damaged. The sockets can wear out over time too. Try changing settings to confirm it, but I'm thinking the contactor is the problem here. Gotta run.

Good luck with it.

Hey Steve,
Thanks for your response.
I'll have a look at the contactor. Just to double check, it's what's in the red circle? this one looks to be 3 pole.

I did run it through some different settings. I went up on the selector to #2 and #3. I also set the wire speed up to 60.

Definitely check the contacts. I had to replace the contactor on my MM210 because they were severely damaged. I have a thread on here somewhere. But it was cheap ~ $25.

Also make sure the female panel / jack plug connectors are still tight as well as wire connections.

Hey Pipeliner,
Thanks for your suggestions. I'm going top check out the contactor.

 

The contactor is probably shot Doug. Pretty common on these types of machines. When the contacts get worn, power cannot fully transfer through it. As power is transferring thru the contacts, the lack of good connection is what causes the buzzing. Sometimes other components inside them come loose and cause excessive noise, but most of the time poor output and loud noise coming from the machine is a classic case of contactor failure/need of service.

I believe it's a two pole, 30 or 40 amp job, with a 24 VAC coil. You can buy a replacement almost anywhere online. I buy them from an HVAC company on eBay for the Maxtrons and they're under $20/ea. You don't need to buy an expensive one IIRC, it's a two pole job, but even a three pole one would work. As long as the configuration is similar and coil voltage is the same, you're good to go.

That's almost a certainty what the issue is. You can even take it apart and dress the contact points to get you by for the time being. It's the component that looks like a big open relay with larger wires running to and from it. And as Burt said, check the pin connections and make sure they're not heavily pitted or damaged. The sockets can wear out over time too. Try changing settings to confirm it, but I'm thinking the contactor is the problem here. Gotta run.

Good luck with it.

 

Definitely check the contacts. I had to replace the contactor on my MM210 because they were severely damaged. I have a thread on here somewhere. But it was cheap ~ $25.

Also make sure the female panel / jack plug connectors are still tight as well as wire connections.

 

I was able to pull the contact points out of mine and clean them up. Made a huge difference. I also took the opportunity to clean all the contacts on the selector, as well as the cable connections. The back side of one of the din plugs is notorious on the machines for having arcing problems. Unbolt and wire brush and retighten.