Thermal arc 250 Fabricator fault finding

[horsey89]

Hi there,

I am fault finding a welding set for a family member, at first the set was not doing anything but I found the neutral or common going to the isolating transformer was 240v down to earth. I have disconnected the three cores of the cooling fan to temporary fix this issue. for some reason the fan has 250v on all three cores which is strange but I have disconnected this completely to continue fault finding the low power output. after this the machine is arcing away like it should but with low power.

I've been using ChatGPT to assist me and it is recommending check the following;

PCB - Cant see any visual damage
Rotary Switch - Visual tests ok got a bit lost checking for ohms when switching - unsure which of the 16 terminals should be switching to which but looks ok and all similar resistance readings.
Power supply - This seems ok now that I sorted the shorted live-neutral fault
Capacitors - I can do this no problem technically its just hard access
Rectifier plates and Diodes - I cant actually see the diodes within the plates so unsure how to carry this test out.
Transformer (main) - Very hard access
Inductor & Coil - Again hard access

I had a look at these visually and they seem ok although dusty but to test them all individually is going to require a full stripping of the machine to gain access and to disconnect each item from the rest. So I just wanted to ask firstly if there is any other common faults that I should be aware of or quicker ways to test the capacitors, rectifiers and main transformer without stripping out to gain access.

Also why has the cooling fan got three cores? and how would I test the fan seeing as its got 240v on all three cores am sure its knackered but would like to confirm, but i dont understand the three cores.

Cheers,
Shaun

 

[horsey89]

Hi there,

I am fault finding a welding set for a family member, at first the set was not doing anything but I found the neutral or common going to the isolating transformer was 240v down to earth. I have disconnected the three cores of the cooling fan to temporary fix this issue. for some reason the fan has 250v on all three cores which is strange but I have disconnected this completely to continue fault finding the low power output. after this the machine is arcing away like it should but with low power.

I've been using ChatGPT to assist me and it is recommending check the following;

PCB - Cant see any visual damage
Rotary Switch - Visual tests ok got a bit lost checking for ohms when switching - unsure which of the 16 terminals should be switching to which but looks ok and all similar resistance readings.
Power supply - This seems ok now that I sorted the shorted live-neutral fault
Capacitors - I can do this no problem technically its just hard access
Rectifier plates and Diodes - I cant actually see the diodes within the plates so unsure how to carry this test out.
Transformer (main) - Very hard access
Inductor & Coil - Again hard access

I had a look at these visually and they seem ok although dusty but to test them all individually is going to require a full stripping of the machine to gain access and to disconnect each item from the rest. So I just wanted to ask firstly if there is any other common faults that I should be aware of or quicker ways to test the capacitors, rectifiers and main transformer without stripping out to gain access.

Also why has the cooling fan got three cores? and how would I test the fan seeing as its got 240v on all three cores am sure its knackered but would like to confirm, but i dont understand the three cores.

Cheers,
Shaun

View attachment 485429 View attachment 485430 View attachment 485431 View attachment 485432

also please ignore the loose core on the transformer I was disconnected outputs to make sure output cores were not causing problems when I was first diagnosing

 

[eddie49]

Hello and welcome to the Forum !

As a first response regarding the unusual fan: there is an additional winding on the stator that effectively uses it as a transformer, providing low-voltage AC which runs the 24v wirefeed motor. This is described in a couple of earlier threads, for the badge-engineered "Cigweld" version:
Post #5 here:

Mig wire feed control board replacement.

Greetings from New Zealand. Electric by trade. Repair Welders as part of job.. Have 2 headaches at the moment. Both involves older model Welders with shot wire feed control boards. Replacements unavailable. Seen a post about generic Chinese boards. Anyone know of a board that does 2t and 4t...

www.mig-welding.co.uk

Post #9 here:

250 Fabricator/CIG 250 TRANSMIG Parts

Hi all. As per my introduction a week or so ago I live in Australia. I am refurbishing a CIG 250 TRANSMIG which (I think) is the same machine as the Thermal Arc 250 Fabricator. Mine is the remote machine with the 2R wire feeder unit. I'm looking at trying to get some important parts put away...

www.mig-welding.co.uk

 

[eddie49]

The white "Atco" isolating transformer is not a normal part of this welder. It may have been added to provide the low-voltage AC that is normally derived from the fan winding.
Do you know the history of this welder? Has it previously been working, and then failed with low penetration?
Can you confirm that it is a single-phase machine, wired to normal 230v AC mains with a 3-pin 13A or 16A plug?
A photo of the dataplate ( if legible ) would be helpful.
( The picture of the rectifier and the presence of the large blue electrolytic capacitors implies that this is a single-phase machine.)
The basic functionality of the main transformer, the rectifier, and the capacitors can be verified with a simple check of the output voltage. With 16 terminals on the rotary switch, the welder probably has 8 power ranges. If you measure the DC voltage between the tip of the MIG torch ( +ve ) and the workpiece clamp ( -ve ), it should step up in equal increments from about 15v to 30v as you rotate the "power" switch.

 

[Shedendman]

Whos needs ChatGPT for stuff like this when you.ve got @eddie49 Top Man

 

[eddie49]

Thanks goes to @Relic who pointed out that the TA Fabricator/Cigweld MIGs use the fan as a "transformer".

 

[horsey89]

Hi Eddie, thanks for your reply I will test the rotary switch properly & look in to the previous posts thanks.
My father in law has had this welding set from brand new and its never had any work done so he's certain the isolating transformer is as per design. it is single phase on a 16a blue plug.

It was running good for years but developed a few problems let me try and explain.

First fault happened was; Reduced power but he was managing to use it for certain jobs with 0.6mm wire. he persevered with this for a couple years. Before this the machine was hardly used just been sitting in his workshop.

Second fault was the three options for modes on the wirefeed motor. one you press nozzle and it runs until you let go, second you press and press again for it to stop and third was something similar to second. The second and third options stopped working but I've followed the cores and this seems to be a problem on the PCB.

Third Fault happened fairly quick after the second fault, and it was that the machine stopped working altogether and the fan stopped coming on when plugged in.

on investigating I found an issue with the fan; The white core coming from fan goes in to the Common on the white safety isolating transformer and the purple core goes in to the top right terminal on the same transformer (nothing on other side of terminal block) i left the blue core going to fan from the Live on coil of contactor therefore putting 240v to the cooling fan and both the white and blue core are alsoputting out 240v to earth. So this was stopping the machine working as it was putting 240v on the white core to Common/Neutral on transformer. I've disconnected this and not looking any further as we would like to fix the low power issue first before deciding to spend time on other faults.

Please see attached some overview photos and one of dataplate. I will check the output voltages on rotary switch soon. If the Rectifiers, capacitors and transformer are working correctly what should the voltage be when turned to lowest and highest setting?

Please see more photos below and one with dataplate.

Thanks for your help