- Thread starter sarahweld
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The contactor itself is OK, the fault is that there's no 24v to pull in the contactor.
This old thread that I mentioned earlier
https://www.mig-welding.co.uk/forum/threads/murex-tradesmig-140-does-not-weld.42345/
has a picture of the PCB. The second picture in post number 12 shows the bridge rectifier. It is the rectangular black plastic component between the two long white plugs. It turns AC into DC. It has 4 pins, marked + , ~ , ~ , and - . The two "~" are AC in, and the + and - are the DC out. With your meter set to the 200v AC, and the machine powered on, there should be about 24v AC between the two "~" pins. On the 200v DC range, your meter should show about 24v DC between the + and the -. It may not be easy to reach these pins with the PCB in place and with power on, so you could solder four short pieces of insulated wire to the solder side of the PCB, to extend the connections outwards so you can reach them.
This old thread that I mentioned earlier
https://www.mig-welding.co.uk/forum/threads/murex-tradesmig-140-does-not-weld.42345/
has a picture of the PCB. The second picture in post number 12 shows the bridge rectifier. It is the rectangular black plastic component between the two long white plugs. It turns AC into DC. It has 4 pins, marked + , ~ , ~ , and - . The two "~" are AC in, and the + and - are the DC out. With your meter set to the 200v AC, and the machine powered on, there should be about 24v AC between the two "~" pins. On the 200v DC range, your meter should show about 24v DC between the + and the -. It may not be easy to reach these pins with the PCB in place and with power on, so you could solder four short pieces of insulated wire to the solder side of the PCB, to extend the connections outwards so you can reach them.
sarahweld
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Thank you for this info . I like to be given a clue as what to do . You have made this sound easy enough for me to do. I think I should be able to do this. I shall return shortly with info also thanks everyone for being so much help
sarahweld
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Afternoon everyone...
Well I've just removed the pcb to solder 4 wires on.. I think I'm going to re solder a lot of the pcb as there looks to be a lot of dry joints. I will do this first then solder the test wires on and get back to you thanks again for the help x
Well I've just removed the pcb to solder 4 wires on.. I think I'm going to re solder a lot of the pcb as there looks to be a lot of dry joints. I will do this first then solder the test wires on and get back to you thanks again for the help x
MattH
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You’re on AC amps and not AC volts on the meter. On a current sensing setting the probes are shorted as they create a current shunt.
Set to V~ To read the AC side (both ~ points) and V—- to read the DC side.
Polarity doesn’t matter, you will just get a minus reading if around the wrong way (only on DC).
Set to V~ To read the AC side (both ~ points) and V—- to read the DC side.
Polarity doesn’t matter, you will just get a minus reading if around the wrong way (only on DC).
sarahweld
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Hiya no cant see a fuse anywhere
Well done with the multimeter action! We got the readings we needed, the meter has not blown up, and you are still alive....!!
Now we know that the auxiliary power supply is OK - there is 24v AC input, and the rectifier turns it to 24v DC to run the PCB.
It looks likely that some electronic component on the PCB has died. From now on, the troubleshooting process is going to get harder - especially since I don't think anyone has a schematic diagram.
I would suggest that you power off and unplug the machine, gently remove the clear plastic cover from the relay on the PCB. Then plug in and switch on, then carefully - e.g. using an insulated screwdriver - press the moving steel part of the relay upwards so that the contacts close. I expect that the welder will turn on and be ready to weld, just as if you had pressed the trigger on the torch. If this is the result, then we need to figure out why the electronics is not turning the relay on.
Now we know that the auxiliary power supply is OK - there is 24v AC input, and the rectifier turns it to 24v DC to run the PCB.
It looks likely that some electronic component on the PCB has died. From now on, the troubleshooting process is going to get harder - especially since I don't think anyone has a schematic diagram.
I would suggest that you power off and unplug the machine, gently remove the clear plastic cover from the relay on the PCB. Then plug in and switch on, then carefully - e.g. using an insulated screwdriver - press the moving steel part of the relay upwards so that the contacts close. I expect that the welder will turn on and be ready to weld, just as if you had pressed the trigger on the torch. If this is the result, then we need to figure out why the electronics is not turning the relay on.
sarahweld
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No there's nothing working when I press the relay apart from it goes louder the fan still isn't turning and I get no wire feed
That's really good news that everything works when you press the PCB relay in manually.
For the next step, I would suggest the following:
1. There is a member of this Forum @NotANormalCoder who may have a circuit diagram. If he has time, he might respond to this "@"
2. As you have found, these guys
https://www.ebay.co.uk/itm/BOC-TRAN...ELDER-CONTROL-PCB-REPAIR-SERVICE/113743613023
will do an exchange repair of the board for £72. That company is TecArc, who make Oxford and Portamig welders.
3. Amongst my 14 welders, I happen to own a BOC Transmig 140. You could send the PCB to me, and I'd be happy to check it out in my welder ( FOC ), and hopefully fix it. It would give me a reason to reverse-engineer the circuit diagram, which may help others in the future.
Edit: Err, was your post 74 a response to Anguz ? I thought that you said pressing the relay on the PCB fixed everything?
For the next step, I would suggest the following:
1. There is a member of this Forum @NotANormalCoder who may have a circuit diagram. If he has time, he might respond to this "@"
2. As you have found, these guys
https://www.ebay.co.uk/itm/BOC-TRAN...ELDER-CONTROL-PCB-REPAIR-SERVICE/113743613023
will do an exchange repair of the board for £72. That company is TecArc, who make Oxford and Portamig welders.
3. Amongst my 14 welders, I happen to own a BOC Transmig 140. You could send the PCB to me, and I'd be happy to check it out in my welder ( FOC ), and hopefully fix it. It would give me a reason to reverse-engineer the circuit diagram, which may help others in the future.
Edit: Err, was your post 74 a response to Anguz ? I thought that you said pressing the relay on the PCB fixed everything?
sarahweld
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I'm still not getting the fan coming on when I touch the relay together my joy was short lived haha and plenty premature, the machine gets louder that's about it . How do I test I the contractor has an open circuit eeeeek thank you
sarahweld
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Pressing the relay just make it sound like id pressed the contractor In manually, the fan jerked but didnt spin and does this everytime I touch contact on the relay.
With the correct power going to the rail on the pcb does jt then,indicate the pcb is dead
When you lift the armature of the relay on the PCB ( without it's plastic case ), I would expect that the contactor will pull in ( clunk ), the welding torch tip & wire will go live ( i.e. you can get an arc ), and the machine would behave as if you had pressed the torch trigger. Is that the situation?
As for the fan, I don't know when to expect it to come on ( i.e. main power switch, or trigger press ), but anyway, are you sure the fan was working before the welder stopped working? Does the fan rotor spin freely if you try turning it by hand without power at all.... maybe it's just sticky.
As for the fan, I don't know when to expect it to come on ( i.e. main power switch, or trigger press ), but anyway, are you sure the fan was working before the welder stopped working? Does the fan rotor spin freely if you try turning it by hand without power at all.... maybe it's just sticky.
sarahweld
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Tested power to l1 and l2 nothing at l3 how do I test an open circuit
sarahweld
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Yes fan was working I've just tested the fan and it works there's no contractor pull or anything apart from the machine sound changes of the machine. But its not as loud as it is when I do press the contractor in manually .
