- Thread starter bloobloo
- Start date
The rectifier on this machine is just "different". Usually the threaded studs are totally insulated from the electrical circuits and are used as mountings. Here the studs conduct, from the transformer secondary to the press-fit diode pairs. The diode anode or cathode pins are spot-welded to thin brass shims held by the nuts, similar to the Siemens rectifiers used in Migatronics.
Instead of the studs, this rectifier is mounted onto a plastic frame by screws through the aluminium plates.
I am concerned by the way that the transformer secondary wires are very messy, with poorly-made connections to the threaded studs, and then apparently returning to the transformer?
Instead of the studs, this rectifier is mounted onto a plastic frame by screws through the aluminium plates.
I am concerned by the way that the transformer secondary wires are very messy, with poorly-made connections to the threaded studs, and then apparently returning to the transformer?
bloobloo
Professional Tinkerer
- Messages
- 271
- Location
- Ashton in Makerfield, Wigan UK
Right then, sorry for the delay. I forgot about Fathers day so had to do the family thing instead of playing in the workshop.
I have disconnected both sets (4) wires from the rectifier. pressed the trigger and......... no fuse blown or breakers tripped. I can hear the "thud" when the trigger is pressed, but the wire feed motor didn't turn, however, i may have turned the speed all the way down, I will check tomorrow.
![IMG_1760[1].JPG](https://www.mig-welding.co.uk/forum/data/attachments/292/292962-b314445f64f3a7fe3e2092c918c96a96.jpg?hash=sxREX2Tzp_ "IMG_1760[1].JPG")
![IMG_1759[1].JPG](https://www.mig-welding.co.uk/forum/data/attachments/292/292966-3ee842afa5031bc7813d5d83976a256d.jpg?hash=PuhCr6UDG8 "IMG_1759[1].JPG")
I have disconnected both sets (4) wires from the rectifier. pressed the trigger and......... no fuse blown or breakers tripped. I can hear the "thud" when the trigger is pressed, but the wire feed motor didn't turn, however, i may have turned the speed all the way down, I will check tomorrow.
bloobloo
Professional Tinkerer
- Messages
- 271
- Location
- Ashton in Makerfield, Wigan UK
Tried turning the wire speed up but nothing happens. tried the switches on the front, the thud from the transformer gets progressively louder as you go up in power on the switches when the trigger is pressed.
What is the next move?
Where should these wires go if they don't belong on the rectifier?
Hutcho, any chance that you could take a closer pic of your transformer to help me figure out where my wires should go please?
What is the next move?
Where should these wires go if they don't belong on the rectifier?
Hutcho, any chance that you could take a closer pic of your transformer to help me figure out where my wires should go please?
That it's not burning out fuses is the important bit. The symptoms indicate that the rectifier has a short circuit so when it's disconnected, the transformer doesn't have any load and so doesn't bur the fuse out. The motor will be powered by the output from the rectifier, without it being connected, the motor will not run.
You can check the motor works by unplugging it from the main PCB and powering the motor from a battery, e.g. a PP3 etc.
You can also check the rectifier out now. Put your test meter onto low ohms range - typically 200 ohms and measure the resistance across the rectifier input. It should be OL or open circuit. Anything near 0 ohms means new rectifier.
The rectifier could be good - but the wires could be wrong so change your meter to a low AC volts range and measure the voltage across the transformer wires you removed from the rectifier. You should get something in the range of 18V to 40V and the voltage should change when you alter the switches on the front of the welder and press the trigger.
It certainly looks funny with that split secondary. It may need a bit of careful voltage testing and labelling of the wires before reconnecting.
You can check the motor works by unplugging it from the main PCB and powering the motor from a battery, e.g. a PP3 etc.
You can also check the rectifier out now. Put your test meter onto low ohms range - typically 200 ohms and measure the resistance across the rectifier input. It should be OL or open circuit. Anything near 0 ohms means new rectifier.
The rectifier could be good - but the wires could be wrong so change your meter to a low AC volts range and measure the voltage across the transformer wires you removed from the rectifier. You should get something in the range of 18V to 40V and the voltage should change when you alter the switches on the front of the welder and press the trigger.
It certainly looks funny with that split secondary. It may need a bit of careful voltage testing and labelling of the wires before reconnecting.
bloobloo
Professional Tinkerer
- Messages
- 271
- Location
- Ashton in Makerfield, Wigan UK
Right, some numbers for you! 1st pic is the ohms as requested. 2nd pic is the voltage when trigger is pressed. I've wrote them on making tape and stuck them to the wires that they relate to. the numbers on the heat shrink is the constant voltage without the trigger pressed.
![IMG_1762[1].JPG](https://www.mig-welding.co.uk/forum/data/attachments/293/293144-9f5ddd1f71ee334f60d3b854fe546357.jpg?hash=n13dH3HuM0 "IMG_1762[1].JPG")
![IMG_1764[1].JPG](https://www.mig-welding.co.uk/forum/data/attachments/293/293145-7fbdd9118b94b597e40204209aeae94f.jpg?hash=f73ZEYuUtZ "IMG_1764[1].JPG")
Those numbers look odd. Can you do some more tests.
Unplug the welder from the mains.
Firstly, the ohms reading, can you do it again but with the top white wire disconnected from the rectifier. I think what you have read is the resistance of whatever those two white wires are connected to so disconnect one of the white wires and try again.
Also, on your meter, turn it to the diode test (very bottom D and diode symbol). This should be better for testing the diodes in the rectifier. Do the following tests with the white wire disconnected and note the following readings :-
1) Red lead on top terminal like in your first photo, black lead on bottom terminal
2) Swap the leads over (Red to bottom, black to top)
3) Red lead on top terminal, black lead on rectifier plate or +ve terminal - the thick wire bolted to the rectifier plate
4) Swap the leads above (black on terminal and red on plate/+ve terminal)
5) Red lead on bottom terminal and black lead on rectifier plate (+ve terminal)
6) Swap them over (black lead on bottom terminal, red lead on rectifier plate +ve terminal)
We should get a good idea from the above whether the rectifier is any good or not.
Now check the transformer :-
Meter to continuity (200 ohm and turn the beeper on on the top right switch).
Short your meter test leads out and make sure it beeps at you and/or reads 0 or thereabouts Ohms.
Pick a lead on the transformer and label it 'A' written on a bit of tape.
Connect one meter lead to transformer 'A' and use the other lead to touch the other three wires. I expect one to beep and two to not beep.
Mark the wire that beeps with another 'A'.
On the two wires that didn't beep, connect one meter lead to one of them and the other meter lead to the other one. They should beep. If they do, mark them 'B'.
Switch your meter to AC 200V. Connect the red lead to 'A' and the black lead to the other 'A'.
Set welding voltage switches to lowest setting,
Connect mains to welder and turn the power on.
Press the torch trigger and note the voltage reading on the meter
Do this for each voltage setting on the welder.
Turn welder off and disconnect from mains.
Connect your meter to transformer wires B and then set switches to lowest setting, connect to mains and check voltages across B wires on all the settings.
I would expect the voltages across A and B windings to be about the same for the same settings.
Let us know how you get on.
There is one more step to do before it bolts back together but that depends on what we find above.
Unplug the welder from the mains.
Firstly, the ohms reading, can you do it again but with the top white wire disconnected from the rectifier. I think what you have read is the resistance of whatever those two white wires are connected to so disconnect one of the white wires and try again.
Also, on your meter, turn it to the diode test (very bottom D and diode symbol). This should be better for testing the diodes in the rectifier. Do the following tests with the white wire disconnected and note the following readings :-
1) Red lead on top terminal like in your first photo, black lead on bottom terminal
2) Swap the leads over (Red to bottom, black to top)
3) Red lead on top terminal, black lead on rectifier plate or +ve terminal - the thick wire bolted to the rectifier plate
4) Swap the leads above (black on terminal and red on plate/+ve terminal)
5) Red lead on bottom terminal and black lead on rectifier plate (+ve terminal)
6) Swap them over (black lead on bottom terminal, red lead on rectifier plate +ve terminal)
We should get a good idea from the above whether the rectifier is any good or not.
Now check the transformer :-
Meter to continuity (200 ohm and turn the beeper on on the top right switch).
Short your meter test leads out and make sure it beeps at you and/or reads 0 or thereabouts Ohms.
Pick a lead on the transformer and label it 'A' written on a bit of tape.
Connect one meter lead to transformer 'A' and use the other lead to touch the other three wires. I expect one to beep and two to not beep.
Mark the wire that beeps with another 'A'.
On the two wires that didn't beep, connect one meter lead to one of them and the other meter lead to the other one. They should beep. If they do, mark them 'B'.
Switch your meter to AC 200V. Connect the red lead to 'A' and the black lead to the other 'A'.
Set welding voltage switches to lowest setting,
Connect mains to welder and turn the power on.
Press the torch trigger and note the voltage reading on the meter
Do this for each voltage setting on the welder.
Turn welder off and disconnect from mains.
Connect your meter to transformer wires B and then set switches to lowest setting, connect to mains and check voltages across B wires on all the settings.
I would expect the voltages across A and B windings to be about the same for the same settings.
Let us know how you get on.
There is one more step to do before it bolts back together but that depends on what we find above.
Those numbers still don't look right. A readings are good, B readings are way too low.
There should be no volts on any of the windings when the trigger is released.
I think there is some confusion with the wires. Can you take a couple of more detailed photos of the transformer especially the fattest wires coming out of it and where they go. See pic below, I noticed the wire circled, can you tell me where both ends of it go ?
![IMG_1765[1].JPG](https://www.mig-welding.co.uk/forum/data/attachments/293/293265-4ca2545673ecbb527f7d59b7b5ca7057.jpg?hash=TKJUVnPsu1 "IMG_1765[1].JPG")
Brilliant
I bet you never measured that with your volt meter
Get a picture of the transformer from the top and also from the side as much detail as possible - include that wire above area as well. That could be part of winding B or it could be part of the choke, difficult to tell at the moment. If it's the choke (i.e. not part of the main transformer) see if you can identify where the other end of it goes to.
From the current images, I can't exactly determine the wires coming out of it, it's difficult with pictures because of the shortening effect, to tell how thick (relatively) the wires are.
These also don't make total sense. Readings 3 & 5 are about what I would expect as the forward volt drop across the diodes, readings 4 & 6 show the diodes reverse voltage, together they say that the diode(s) being measured are good.
Readings 1 and 2 show a dead short circuit between the terminals. When you measured it, were you measuring across the two connectors as circled below and the transformer wires were disconnected from them ?
Can you also take some detailed pics of the rectifier.
I'm coming round to the earlier theory that the welder has been incorrectly re-assembled and the output from the transformer is wired incorrectly and is short circuited.
I believe that the solid "copper-coloured" wire at the back of the rectifier is bolted to the negatve output plate of the rectifier, and this wire is the winding of the inductor. The other end of the inductor connects to the work return lead and work clamp, and the inductor has a very low resistance so it seems like continuity. The inductor is wound on a plastic bobbin on the same core as the main welding transformer.
