Hi all,
Newbie to this site here! I was hoping somebody on here might be able to advise me on a problem I have with my welder.
I bought the set (Migmate Super 110) secondhand maybe 20 years ago and used it quite successfully to patch a succession of cars up. I wasn't aware at the time that there were problems with the SIP range so I just got on with it; a bit like the bumblebee, which scientists have determined is physically unable to fly due to its body shape being all wrong, its weight too high and its wings too short. Problem is, nobody told the bee . . . OK, the wire feed may have been a little finicky, but nothing I couldn't put up with.
Anyway, I got fed up with working on cars outside in all weathers and bought a newish car about 12 years ago, and have never felt the need to get under a car since then. Call it old age
I now suddenly have a need for a MIG set though, so the other day I foraged in the furthest corners of The Shed and hauled the old SIP out into the harsh light of day. First things first; I plugged it in and . . . . absolutely nothing. Had a couple of flicks of the switch and the neon finally lit up, but nothing else (when I was using it regularly I 'turbolised' it with a 4" fan to extend the duty cycle a bit (worked, too!)) The fan is connected to come on when the mains switch is 'on' but didn't on this occasion. I came inside and made a brew and then tried it again - it worked, and this is why I have a profound belief in the power of tea. On pressing the trigger I was rewarded with a click, but nothing else. It started raining then, so I gave up for the time being and made some more tea
Yesterday I put the machine on the bench and decided that I would fix it, come what may. I took the covers off, plugged it in and pressed the trigger again. I got the same click: I could see the relay on the wire feed PCB moving but no action out of the welder. I stripped the wire feed mechanism out and removed the motor, which seemed free to turn. Just in case it was infested with spiders or something, I gave it a shot of WD40 and hooked it up to a 12v power supply and it started up OK, so I replaced it on the gearbox and tried it again with the 12v, when the feed roller spindle turned OK. As an experiment, I put my multimeter across the wires from the PCB to the motor and when I pressed the trigger I obtained no reading on the DC scale, but a constant 20v on the AC scale. Maybe the rectifier diodes have gone duff - I'll check that at a later date. While I was doing that I turned the wire speed control knob up and was surprised that it kept on going round and round but a quick glance under the cover showed me why. The back of the potentiometer had become detached, allowing the shaft complete rotation. I guess something heavy must have somehow managed to get on top of the welder in The Shed and attacked the pot.
I can't see much point in going any further at this stage until I've replaced the pot, but sadly it has no markings on it. I have a suspicion that I may have replaced at some point in the dim and distant past because the soldering on it looks familiar so I guess it must be mine . . .
Can anybody please tell me a typical value for the potentiometer, and whether it's linear or logarithmic? My guess is linear, since it's not an audio circuit, but if I'm going to replace it I might as well do it right.
I'll probably be back with more problems soon; thanks in anticipation for any help with this one.
Newbie to this site here! I was hoping somebody on here might be able to advise me on a problem I have with my welder.
I bought the set (Migmate Super 110) secondhand maybe 20 years ago and used it quite successfully to patch a succession of cars up. I wasn't aware at the time that there were problems with the SIP range so I just got on with it; a bit like the bumblebee, which scientists have determined is physically unable to fly due to its body shape being all wrong, its weight too high and its wings too short. Problem is, nobody told the bee . . . OK, the wire feed may have been a little finicky, but nothing I couldn't put up with.
Anyway, I got fed up with working on cars outside in all weathers and bought a newish car about 12 years ago, and have never felt the need to get under a car since then. Call it old age
I now suddenly have a need for a MIG set though, so the other day I foraged in the furthest corners of The Shed and hauled the old SIP out into the harsh light of day. First things first; I plugged it in and . . . . absolutely nothing. Had a couple of flicks of the switch and the neon finally lit up, but nothing else (when I was using it regularly I 'turbolised' it with a 4" fan to extend the duty cycle a bit (worked, too!)) The fan is connected to come on when the mains switch is 'on' but didn't on this occasion. I came inside and made a brew and then tried it again - it worked, and this is why I have a profound belief in the power of tea. On pressing the trigger I was rewarded with a click, but nothing else. It started raining then, so I gave up for the time being and made some more tea
Yesterday I put the machine on the bench and decided that I would fix it, come what may. I took the covers off, plugged it in and pressed the trigger again. I got the same click: I could see the relay on the wire feed PCB moving but no action out of the welder. I stripped the wire feed mechanism out and removed the motor, which seemed free to turn. Just in case it was infested with spiders or something, I gave it a shot of WD40 and hooked it up to a 12v power supply and it started up OK, so I replaced it on the gearbox and tried it again with the 12v, when the feed roller spindle turned OK. As an experiment, I put my multimeter across the wires from the PCB to the motor and when I pressed the trigger I obtained no reading on the DC scale, but a constant 20v on the AC scale. Maybe the rectifier diodes have gone duff - I'll check that at a later date. While I was doing that I turned the wire speed control knob up and was surprised that it kept on going round and round but a quick glance under the cover showed me why. The back of the potentiometer had become detached, allowing the shaft complete rotation. I guess something heavy must have somehow managed to get on top of the welder in The Shed and attacked the pot.
I can't see much point in going any further at this stage until I've replaced the pot, but sadly it has no markings on it. I have a suspicion that I may have replaced at some point in the dim and distant past because the soldering on it looks familiar so I guess it must be mine . . .
Can anybody please tell me a typical value for the potentiometer, and whether it's linear or logarithmic? My guess is linear, since it's not an audio circuit, but if I'm going to replace it I might as well do it right.
I'll probably be back with more problems soon; thanks in anticipation for any help with this one.
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