Supermig 185 weak wire feed?

[charlysays]

I'm having issues with my sealey supermig 185 wire feed.
It's got so little torque the wire just stops against the slightest resistance, this is leading to it burning back at the tip and putting a lot of heat into the nozzle.
Is it possible to replace the brushes in the motor or do I need an entire new wire feed unit?
There aren't any issues with the rollers slipping etc, the motor just stops against the slightest resistance.
Any advice much appreciated!

 

[mike 109444]

It may be possible to replace the brushes (but would be unusual to need to in a mig). It could be that the driver circuit is at fault. A way to check would be to disconect the motor from the pcb and feed 12v DC to the motor from a battery or power pack. With the wire feed pinch roller fliped up, try rubbing a gloved (leather glove) finger against the feed roller. With the gearing that is used on mig feed motors you should not be able to stop or slow the motor. If the motor does not slow then you most likley have an issue with the drive pcb circuit. if you can slow or stop the motor then the brushes or motor it's self is suspect.
I work on machines that use lots of these small 24v DC geared motors and they run for hours and it's a good few years before they need replacing !

 

[charlysays]

It may be possible to replace the brushes (but would be unusual to need to in a mig). It could be that the driver circuit is at fault. A way to check would be to disconect the motor from the pcb and feed 12v DC to the motor from a battery or power pack. With the wire feed pinch roller fliped up, try rubbing a gloved (leather glove) finger against the feed roller. With the gearing that is used on mig feed motors you should not be able to stop or slow the motor. If the motor does not slow then you most likley have an issue with the drive pcb circuit. if you can slow or stop the motor then the brushes or motor it's self is suspect.
I work on machines that use lots of these small 24v DC geared motors and they run for hours and it's a good few years before they need replacing !

Nice one for the info! I'll give that a try and report back.
The machine looks quite old and battered and was used by a guy making log burners before I had it so I reckon it's done a lot of work. I've had it heading on 10 years and done a lot of work with it too.

 

[mike 109444]

Further info

 

[charlysays]

Further info

Thanks dude.

Here's a vid of me trying to stop the motor. No way I can stop it but by pressing hard I can slow it down.
It's directly connected to an old AGM battery from a jump pack, showing 12.85 volts on the meter.

It also slowed noticeably when I tried getting it to push mig wire into a flat surface.

I don't know how the circuit works but I'm assuming that the motor is just given less volts when you want a slower wire feed.
If the torque is a bit on the low side even at full tilt does this explain why the torque is totally insufficient at low wire speeds?

Thanks again

 

[mike 109444]

Well from that video it looks like the motor has plenty of grunt !
This implys that the circuit driving it from the pcb maybe wherer the issue is.

 

[charlysays]

Well from that video it looks like the motor has plenty of grunt !
This implys that the circuit driving it from the pcb maybe wherer the issue is.

Good to know, thanks for the help
I've kinda got it welding ok after playing with the preload on the spool,greasing the spool shaft and messing around with the wire speed.

I took the control PCB out and gave it a good clean. No obvious issues. Timer works, wire speed control works consistently, it's just the torque from the motor at low speeds is abysmal.
Maybe it always was, but it won't move the wire at 2 and I'm sure it used to.

At full speed the motor has almost as much power as when I power it directly with a battery so the top of the scale on the control board is working ok.

I'll see how it goes and consider sending it off to K Edwards in Staffordshire along with the schematic above.
Thanks again for the help