NBC mig autoweld 140 not working

[Fox2511]

Hi all, This is my first post on here so have patience!
I have an NBC mig autoweld 140 which has been a usefull welder for my needs, but it has stopped working. When I press the switch to weld most of the 'contacts' including the main one snick to make contact but the gas valve doesn't turn on or the wire feed motor but there is an electrical hum. The welding wire does become live.
I have checked the voltage going to the gas valve which reads 145 volts, but I quess it should be 230. I would be very pleased if any one can suggest in simple terms how to find what may be wrong with this machine or failing that to suggest a suitable replacement machine. Norman

 

[the snooper]

if there is a humming it sounds as though you rectifier may have gone
is it a loud humm / buzz

 

[Fox2511]

Many thanks for your prompt reply. The noise is loudish hum. If a rectifier is gone does this affect the power supply to both the gas valve and the wire feed motor? How do I test to prove it is the rectifier? Or are there some other checks I can make with a normal test meter?
In respect of a replacement welder I forgot to say I have three phase supply in my workshop if that affects the choice of welder. Norman

 

[the snooper]

you can remove the rectifier and test the diodes on it with a normal test meter just incase you dont know a diode only passes power in one direction.
most of the small diy welders use the output from the rectifier for the wire feed motor

rectifiers are available and as long as it has the same rating and mounting features it doesnt have to be from the maker of your machine

you can also disconnect one of the feeds to the rectifier and try it again if a diode has gone short circuit it wont buzz with it disconnected

 

[the snooper]

have a look here
there is a wiring diagram for the machine if it helps

i would test the rectifier as a starting point as they usually make the welder buzz loudly when shorting out

 

[Robotstar5]

A hum or buzz could be the main contactor not going in properly, had a couple do that at work.

 

[Fox2511]

Many thanks to all who have tried to help. I have sprayed contact cleaner on all the contacts, including the main one and now the gas valve opens normally, incidentally still at 145 volts, but the wire feed motor does not turn.
I have checked the 4 diodes, all seem the same just allowing current to flow one way.
When I have time I will see what voltage, if any, is going to the feed motor.
Could someone tell me which part is the rectifier? Norman

 

[the snooper]

if you have checked the four diodes in the picture then you have found the rectifier

 

[Robotstar5]

I have sprayed contact cleaner on all the contacts, including the main one and now the gas valve opens normally, incidentally still at 145 volts, but the wire feed motor does not turn.

Contact cleaner will not help a burnt contact which may have a high resistance

 

[Fox2511]

NBC140 mig autoweld wire feed not working.

Hi all, further to previous posts, After some testing I have found that my parvalux wire feed motor has died. . If anyone has a parvalux motor that works that I could buy please reply, I will keep my fingers crossed . All the best, Norman.

 

[Drains]

Fox, this thread has already been there.

You may have to speak to Parvalux.

 

[Robotstar5]

What does a Parvalux motor look like? I've got an esab/murex one spare.

 

[madkayaker]

shiney

 

[Drains]

shiney

Oh come on MK. If that's all you're going to say, really, don't bother pal, just keep it to yourself, eh?