Miller Shopmaster 300 MIG problem

M.B. Naegle · May 1, 2020

I've been having a problem MIG welding lately. Our machine is a single phase Miller Shopmaster 300, with a 22A wire feed unit, .035 wire, and N.O.S. gas. The trigger activates the gas and wire just fine, but if you touch the wire to the grounded metal, it pops like the trigger isn't gating the current.

I'm thinking it has something to do with our connections? I was having other issues and found that the polarity was backwards, so it's correct now (positive to trigger, negative to clamp) but still having the popping issue. I've been working around it as it welds fine once I get going, it's just touchy to start. It doesn't seem to change between different materials and settings. Nearly everything we do with it is mild steel from .060" to .250" thick.

We also have a High Freq. TIG unit set up with it too. Part of my problem is that my Dad (who's deteriorating with age

) keeps trying to weld but forgets which switches are supposed to be where and assumes that components are faulty. I've been trying to keep it sorted out (and keep him out of trouble) and have found that nine times out of ten, the "broken welder" ends up having a lead connected wrong or some other simple thing, so I'm hoping that it's the case here too.

doug8cat · May 2, 2020

During my graduate studies we dealt with memory and all that good stuff. I still read some journals and just a while ago an articles on the beginning stages of dementia.
A lot of folks much smarter than yours truly use colors for patients struggling with memory problems.
So here is my .02:
Cables - use colored tape on the cable connector and jack i.e. green tape on cable and green tape on jack.
Switches - tape off ones that very change. For others maybe make him a simple chart that states for example:
Stainless then list what switches need to be in what position.
I feel bad for you both, I have gone though watching friends and loved ones slowly succumb to dementia and is not easy. It sounds like you love him very much, but as I said it is sometimes frustrating; patients is the key. The fact that he is still working is great the more active the brain the better. Also by giving the paper list and color coding the cables it lets him maintain his independence to a degree, that alone should make him mentally feel better.

Regards,
D

dana gear · May 2, 2020

The 300 is a dirt simple power source and the 22A is a great industrial feeder. Check ALL cable connections then check that the electrode wire will coil up in your gloved hand held about 7 inches from the contact tip, if it does not then check drive roll tension and correct drive roll size. .035 wire I am assuming in the ER 70-S -6 range? electrode positive and the work negative.
If your power source has the optional meters then with .035 you want to see around 18.5-19 volts and when welding around 145 amps.
If no meters then you can use a simple DC volt meter at the output studs. With the electrode wire feeding through the gun there should be very little restriction with the gun played out straight, if there is then there could be a problem with a damaged liner, wire feed should be smooth, you should never have a jerkey wire feed. Be sure all remotes are switched to "panel"
The Shopmasters are decent Constant voltage/constant current power sources, the problem was that Miller Electric was trying to build a multi process power source and to keep the price where it would be marketable, so some concessions had to be made and in doing so the Constant voltage side was pretty good but not great. they do although not often have problems with the PC board PC-1 or the hall amplifier. At one time we had 8 of these power sources.

M.B. Naegle · May 4, 2020

doug8cat said:
During my graduate studies we dealt with memory and all that good stuff. I still read some journals and just a while ago an articles on the beginning stages of dementia.
A lot of folks much smarter than yours truly use colors for patients struggling with memory problems.
So here is my .02:
Cables - use colored tape on the cable connector and jack i.e. green tape on cable and green tape on jack.
Switches - tape off ones that very change. For others maybe make him a simple chart that states for example:
Stainless then list what switches need to be in what position.
I feel bad for you both, I have gone though watching friends and loved ones slowly succumb to dementia and is not easy. It sounds like you love him very much, but as I said it is sometimes frustrating; patients is the key. The fact that he is still working is great the more active the brain the better. Also by giving the paper list and color coding the cables it lets him maintain his independence to a degree, that alone should make him mentally feel better.

Regards,
D

He's marked up the machine pretty good... several times, to the point that I think it had gotten confusing. It had "mig" and "tig" written in too many places to be any help, so one thing I did is go over it cleaning off all the sharpie marks and filling in all the dremel etching. I'm making some step by step charts for him using the actual switch names and nomenclature and adding colors to it would help. I do a fair amount of MIG but not often enough to have gotten good at it, so I'm hoping we can use it as an opportunity to help us both improve.

He has good days and bad days, to varying degrees. From a "business" perspective there are days I want to just tell him to go home, but I know that would ultimately make things worse. Family business takes a whole different level of education that you can't seem to find anywhere but through experience.

M.B. Naegle · May 4, 2020

dana gear said:
The 300 is a dirt simple power source and the 22A is a great industrial feeder. Check ALL cable connections then check that the electrode wire will coil up in your gloved hand held about 7 inches from the contact tip, if it does not then check drive roll tension and correct drive roll size. .035 wire I am assuming in the ER 70-S -6 range? electrode positive and the work negative.
If your power source has the optional meters then with .035 you want to see around 18.5-19 volts and when welding around 145 amps.
If no meters then you can use a simple DC volt meter at the output studs. With the electrode wire feeding through the gun there should be very little restriction with the gun played out straight, if there is then there could be a problem with a damaged liner, wire feed should be smooth, you should never have a jerkey wire feed. Be sure all remotes are switched to "panel"
The Shopmasters are decent Constant voltage/constant current power sources, the problem was that Miller Electric was trying to build a multi process power source and to keep the price where it would be marketable, so some concessions had to be made and in doing so the Constant voltage side was pretty good but not great. they do although not often have problems with the PC board PC-1 or the hall amplifier. At one time we had 8 of these power sources.

Come to think of it, we did replace the gun and cable assembly a while back, so It could be something was connected wrong? It feeds in pulses at times, so there's definitely something wrong. I don't remember if the the problem started with the new gun, but I think we still have the old one so I'll see if there's anything different between them.

M.B. Naegle · May 4, 2020

Ok, so the feed inconsistency was an easy fix. There was some grit/oil on the wheels and the tension was maxed out. I cleaned the wheels and backed off the tension and it's feeding consistently. I still need to plug in a meter and check the voltage.

I found some other threads/forums about my main issue: it arcs before pulling the trigger, however the trigger activates the gas and wire feed just fine. In the other cases the solution was a stuck/bad contactor. So now I'm trying to figure how to swap that part out on the 22A wire feeder(?).

M.B. Naegle · May 4, 2020

Problem Solved!

I was trying to find the contactor for the lead in the Wire Feed unit, then realized it wasn't in there, it was in the main power supply, and that it had an on/off switch.
:dunce:

So the contactor was simply turned off such as you would have for stick welding. I didn't think of this because next to the switch it had "TIG (down arrow)" etched and we absentmindedly thought MIG must be the other way.

My dad hugged me when I showed him as he remembered that step of the settings. He has loads of experienced that are held back by an old mind. I've got much less experience in a spry young mind, so we'll keep working together and get a process worked out that we can both understand. We used to do loads of welding a few years back but lately it's been more on-demand for parts repair and such, so I've got to get some notes together to keep us on track when I've been away from the welding table for too long or he's having a hard day.

dana gear · May 4, 2020

Glad you got it going, Just remember that stick welding (SMAW) constant current will require contactor on and that if your using a remote control for GTAW welding then switch from panel to remote. If no remote used then switch from remote to panel.

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