Murex 245

[JohnHodgson]

I have a murex 245 single phase welder which is probably 30 years old.
When I press the trigger the wire feeds but no gas or anything else happens.
What do you think is the problem?

 

[Pilgrim22]

Is the gas bottle 30 years old also?

 

[Radar 3]

Is the gas bottle 30 years old also?

Is the machine in continuous,spot and stitch off.

 

[JohnHodgson]

This machine doesn’t have a mode selector like the 285 machine.

 

[Radar 3]

Just had a look and the 245 can spot/stitch weld.

 

[eddie49]

I guess that the torch trigger switch makes the circuit for a small relay on the printed circuit board, which then enables the Contactor. This heavy-duty relay feeds mains power to the welding transformer. There is usually a manual operating button in the centre of the top of the contactor. Try pressing this button, e.g. with an insulated screwdriver, and check if you can strike an arc at the tip of the MIG wire.

 

[Bravheart]

Hi John this welder should have a spot stitch continuous switch on the panel.

This problem was covered in the boc/murex help, faults thread and a new capacitor somewhere cured it, there is also a manual to download on this thread.

Murex 235 Tradesmig Problem

After fitting new fuses welder still does not spark. Lights up when switched on and wire feeds but will not spark. I have cleaned and checked the earth cable/clamp which is fine. Anybody got any ideas?

www.mig-welding.co.uk

 

[Monkey Harris]

I have a murex 245 single phase welder which is probably 30 years old.
When I press the trigger the wire feeds but no gas or anything else happens.
What do you think is the problem?

Is the contactor pulling in...
Mine stopped ,
it was the contactor coil...
Got a vintage one on ebag.. £10..

 

[eddie49]

There are references to this single-phase Murex 245 problem getting posted on an old thread about the 3-phase model 235 here:

Murex 235 Tradesmig Problem

After fitting new fuses welder still does not spark. Lights up when switched on and wire feeds but will not spark. I have cleaned and checked the earth cable/clamp which is fine. Anybody got any ideas?

www.mig-welding.co.uk

However, I think we should continue this 245 discussion in this current location.

For the record, this is my update:

There are Murex Tradesmig circuit diagrams here:
http://murex-welding.co.uk/manuals/other/Instruction Manuals/Tradesmig 165-235-245-285.pdf
The diagram for the single-phase 245 shows that the solenoid coil of the gas valve is in parallel with the operating coil of the Contactor. When the electronics on the PCB tells the Contactor to pull in, the gas valve will also open.

However, on your machine it looks like the Contactor is not getting the signal to pull in, so to test what is going on, we can push it in manually. That will help to diagnose where the fault is. With the machine plugged in, switched on, the torch trigger squeezed, then the manual button on the Contactor held in with a screwdriver, you should get wirefeed running and an arc at the wire tip. I don't think the gas valve will open, but let us know if it does. This test will help to decide if it is the operating coil of the Contactor that is burnt out, or the electronics on the PCB.

This old thread from 2019 is for the 3-phase model 235, I think it would be clearer to continue this discussion in your new thread for the single-phase 245.

Your machine does have 6 large capacitors across the welding output, but the machine in this thread, the 235, does not have any. Being a 3-phase machine the output is already smoother, and does not need capacitors, so I don't understand the solution that was referred to in Nov. 2019.

 

[eddie49]

This new thread is for the single-phase Murex 245. I think we should continue discussing the problem here, rather than on the old 3-phase 235 thread.
I'm not sure if the small relay on the PCB operates when you press the torch trigger? Perhaps I haven't asked before.

From the circuit diagram, both the gas valve and the contactor run on 220v AC, which is tapped off from the 240v primary of the auxiliary power transformer. The 220v AC is switched by the small relay on the PCB, via pins b1 and b2 of the board connector. The relay may be in a clear plastic case, so you may be able to see it move inside. If the case is not transparent, perhaps you can hear or feel it click inside the case when you squeeze the trigger.
( No need to do the "insulated screwdriver pressing the Contactor button" for this test.)
If the relay operating lever does move, you need to check if the contacts are clean and making good contact. To do that, power off and unplug the welder, then carefully prise the case off the relay and check for any signs of arcing or burning. The contacts can be cleaned with a diamond file or fine wet&dry abrasive paper.

 

[JohnHodgson]

I have looked at the relay on the POV and nothing happens when the trigger is pressed,
The contacts do not seem burned or any signs of arcing

 

[eddie49]

The signal from the torch trigger goes to the printed circuit board, where it should start the wirefeed motor, and activate the small relay, which then powers-up the gas valve and the large Contactor.
The fact that the wirefeed motor does run means the signal does reach the board, and manually pushing the button on the Contactor makes the actual welding transformer power up ( arc is OK ), so I am quite sure that the fault is on the PCB.

There is a mail-in repair service for those boards, run by the company TecArc:

MUREX TRADESMIGS / BRITWELD / ELAND MIG WELDER CONTROL PCB REPAIR SERVICE | eBay UK

MIG WELDER PCB REPAIR SERVICE. We can repair PCB`s out of most makes and models of welding machines and plasma cutter, including inverter welding machines. TEC ARC is a leading manufacturer and repair centre of arc welding machines.

www.ebay.co.uk

To continue troubleshooting and hopefully fixing your board:

If the contacts are clean, the fault may be a burned-out coil on the small relay, or a fault in the component that drives it ( a transistor ). If you can get the case off the relay, and access it safely whilst the welder is powered up, try operating the metal lever ( the armature ) of that relay, so that the contacts close. Take care because those contacts carry live mains - use an insulated tool.
With power on, operating that relay manually will close the contacts and feed mains to the Contactor and the gas valve. You should hear the Contactor pull in.
A photo of your board would help with further troubleshooting.