Dead contactor ? BOC mig 250C

[devlin maguire]

Can anyone tell me when the contactor energises is when it is to connected to the mains or when the panel switch is operated I have tested the connectors at the torch at machine end and have continuity at the two spring loaded pins when the trigger is pressed,however the contactor does not engage, if I push in the contactor I can hear the coils hum but nothing else, I get no volts at the the L/N to the contactor so I suspect the PCB may be duff any thoughts

 

[carbon]

There should be resistance between the a1 and a2 contacts on the contactor. Best to check with at least one of the wires disconnected. Should have the coil voltage marked on the contactor

 

[devlin maguire]

thanks its a 24v dc contactor i will check the coil resistance

 

[devlin maguire]

It is now the case that the transformer is not producing 24 V DC I get continuity through the dc coil and the ac coil, its getting 230 V AC at the terminals, I may remove it and put it on the bench and test it on a known supply, I think its duff so where can I get a replacement cheers
DM

 

[carbon]

The transformer won’t output dc, there needs to be a rectifier some where. Disconnect the incoming supply to the transformer and test the winding for continuity, shouldn’t be open circuit should have some resistance. Do the same in the secondary side of the transformer. Hopefully the transformer will have some information on it to help identify it

 

[devlin maguire]

its a kemppi 9777803 I can't find any info as to the coil resistances, would the rectifier be on the pcb or remote
DM

 

[carbon]

Don’t know any specific resistances but must have some, if windings are open circuit then transformer would need replacing. As to where the rectifier is a wiring diagram would help or at least a few pictures

 

[devlin maguire]

The tranny I am on about only supplies the contacter its not the big welding jobby 230V goes into the tranny and 24V comes out and goes to the A1 A2 cant see where the rectifier might be

 

[Luke]

Can you post some photos of the control board, small transformer and contactor? They'd help a lot.

 

[devlin maguire]

Not at home right now I will update ASAP

 

[NotANormalCoder]

Contactor is controlled by the PCB on this machine (same as most welders), so 240v comes from mains supply where it is connected to the contactor, into a small transformer that supplies the PCB with 24V (AC). I have a circuit diagram for this machine which I will happily email if you PM me with your email address. This may help you resolve your issues. Check output of the small auxilliary transformer, as I have seen a lot of these fail. Should get 240V in and 24V out when machine turned on. Connections are fairly obvious.
Dave