Multi mig 251 torch stays hot

[Nosparksparky]

Hi I have a multi mig 251 the torch stays hot after releasing the trigger I have changed the contactor When I turn it on and pull trigger the contactor engages but does not release any ideas thanks

 

[500e]

Is that a Duralloy MM251 is wire still running
Check To see if control voltage is on contacter coil when torch sw is not engaged
(sticky contactor) OR are there 2T/4T/4ST/Spot trigger modes

 

[eddie49]

Hello and welcome to the Forum.
As 500e suggested, does your welder have Spot, Stitch, 4T, or variable Burnback modes? If so, operate the controls for those functions on and off a few times, then ensure that they are all "Off" and test normal welding mode again.
Is is only the arc that stays "hot", wirefeed and gas solenoid stop on trigger release?
Please post some general photos of the machine, the dataplate, and the control PCB, so that we can identify what make & model it actually is.

 

[roofman]

talking rubbish here..so deleted

 

[Nosparksparky]

Hi thanks for your replies I will get a couple of pics when I get home later this week It has the settings spot burn back etc so I will try them aswell thanks again

 

[Nosparksparky]

Yes it's only the arc that stays hot( I think) I will check your suggestions and report back

 

[Nosparksparky]

 

[Nosparksparky]

Had a fiddle with the controls still the torch is staying live after releasing the trigger contactor staying energised wire and gas stop any suggestions greatly appreciated Thanks

 

[eddie49]

That is an impressive-looking machine, with 18 voltage steps, and Spot and Stitch modes!
It is not a make or model that I am familiar with. It could really be British-made - because of the spelling of the word "Programme".
Do you have any literature, a manual or circuit diagram?

Something must be faulty in the control logic on the PCB, so that the drive for the contactor remains enabled. What is the voltage of the operating coil of the contactor? It could be 12v, 24v, 42v, 48v, AC or DC, or AC mains. Knowing that would help to decide how it is switched on & off, e.g. by a small relay, a power transistor, or a TRIAC.

The next step would be to trace the wires from the contactor operating coil to the PCB, and identify which pins or terminals of the board they connect to. Then from clear photos of both sides of the PCB we can start to reverse-engineer the circuit diagram.
Alternatively, from a photo of the component side and with a list of the device numbers of the high-power semiconductors ( basically, those on heatsinks ) we can guess which one might drive the contactor, and replace that component speculatively.

 

[Nosparksparky]

I don't have any circuit diagrams or manual for it it's 42v coil in the contactor I replaced the contactor I will get some more pictures I will whip the control panel out and take some pictures thank you for your help