Pro mig 170 problem

  1. Damo8 New Member

    Messages:
    4
    Location:
    Sussex
    My pro mig 170 has decided to misbehave, initially the gas stayed running & the wire stayed live without pulling the trigger. I tested a few items with the multimeter and discovered that the finder relay 45/69 was stuck. I then discovered that this is a common fault and replacing the relay with a new 45/71 should do the trick. Having replaced the relay on the pcb, I now cannot get any life when pulling the trigger, the fan runs when I turn the machine on but when I pull the trigger nothing happens. If I short the relay contacts across it goes back to the gas on, live wire etc and if I then pull the trigg the wire spool runs? Any ideas as I'm getting desperate now Any info appreciated.
     
  2. mike 109444

    mike 109444 Member

    Messages:
    4,264
    uk Bristol
    You have not fitted a 24v (48 or more) relay in where a 12v relay should be have you ?
    If trying to drive a relay with a higher rated coil may result in the relay not pulling in.
    Failing that then post pic of pcb so we can sus what is driving the relay coil
    And welcome BTW :hug:
     
  3. Damo8 New Member

    Messages:
    4
    Location:
    Sussex
    Hi Mike
    Thanks for taking the time to reply.
    The relay I replaced is 24v same as the old one, I did check all the markings on the new relay to be sure and it is all correct.
    I have attached pics of the pcb with the new relay fitted as requested.
    Thanx again.
    image.jpeg image.jpeg image.jpeg
     
  4. Seadog

    Seadog Forum Supporter

    Messages:
    6,680
    Location:
    NE London - UK
    Just an observation, and difficult to see from the photo, but the joints to the coil look a bit suspect, especially the ledt one. Also the relay should be mounted flat to the PCB to prevent any damage to the track. I'd desolder it, and start again. Make sure eerything is clean and tin the pins if necessary. It looks like the iron may have been a bit cold when you soldered the new relay in as the solder doesn't seem to have whetted the pins.
     
  5. mike 109444

    mike 109444 Member

    Messages:
    4,264
    uk Bristol
    What made you select that relay ?
     
    • relay 45_71.jpg
  6. Damo8 New Member

    Messages:
    4
    Location:
    Sussex
    In my naivety I just looked up a finder relay 45/71, I read online that the original finder relay 45/69 was no longer available and that the 45/71 from RS was a direct replacement, is this relay incorrect?
     
  7. the snooper

    the snooper getting older by the day

    Messages:
    20,590
    Location:
    Hull UK
    As long as the coil voltage is correct and rated current it will be fine
     
  8. Damo8 New Member

    Messages:
    4
    Location:
    Sussex
    Ok it's fixed , sea dog you were correct, my inferior soldering skills were the problem. I had a friend look at the pcb (they repair radio pcb,s for a job) and she said that the pcb had a track on the top side, that you could not see unless you held it up to the light, aswell as the obvious track on the bottom and that the solder had to flow through the board to make the top track connect with the pins. This is easy on the male connector end of the relay as you can access both sides but much less obvious on the pin end. So resoldered the joints more thoroughly on the pin end and 'voila' it all works great.
    Thanx to all that replied and hopefully this may help someone else.
     
  9. Seadog

    Seadog Forum Supporter

    Messages:
    6,680
    Location:
    NE London - UK
    Glad it's sorted Damo8. More surprised that I managed to spot the problem :clapping:

    I think you were lucky, from what you're describing it sounds as though the board has plated through holes. This is an expensive process and it is surprising if they've been used on a welder PCB. They're extremely easy to damage, i.e. the through plating, which is a tube of copper connecting the upper and lower tracks, can easily be pulled out if the soldered joint has not been totally desoldered.
     
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