Hi guys,
I have an MMA welder that needs repaired (Clarke AT132). The fault is that the low voltage circuit has failed in spectacular fashion. It is a flyback converter to provide the low voltage for the fan, main voltage relay and the inverter pulse controller.
Due to a shorted mosfet, there is significant damage to many smd components as well as the transformer.
Now in my limited wisdom, i thought that i could completely bypass the converter by using a stand alone power supply (18v dc laptop). The pulse controller uses a 15v regulator and i have used a 7812 voltage regulator to power the relay/fans. Powering this configuration up works perfectly on its own.
however, i then connected the power supply to the welder 240v input, thinkin that all would be well….
But once connected like this and power applied to the welder the RCD for the garage is taken out.
So my question is why? What am I missing?
I did find that the ground connector for the 15v regulator went to the -ve side of the bulk capacitor (330v DC here). Is this the cause? Would i require a seperate ground connection for this to work if at all?
But why would that have worked with the flyback configuration?
Now this welder is dirt cheap and not worth fixing really, but i wanted to try for my own curiosity.
But now i would like you guys to educate me as to why this doesn’t work.
What am I missing?
Thanks in advance… and go easy on me.
I have an MMA welder that needs repaired (Clarke AT132). The fault is that the low voltage circuit has failed in spectacular fashion. It is a flyback converter to provide the low voltage for the fan, main voltage relay and the inverter pulse controller.
Due to a shorted mosfet, there is significant damage to many smd components as well as the transformer.
Now in my limited wisdom, i thought that i could completely bypass the converter by using a stand alone power supply (18v dc laptop). The pulse controller uses a 15v regulator and i have used a 7812 voltage regulator to power the relay/fans. Powering this configuration up works perfectly on its own.
however, i then connected the power supply to the welder 240v input, thinkin that all would be well….
But once connected like this and power applied to the welder the RCD for the garage is taken out.
So my question is why? What am I missing?
I did find that the ground connector for the 15v regulator went to the -ve side of the bulk capacitor (330v DC here). Is this the cause? Would i require a seperate ground connection for this to work if at all?
But why would that have worked with the flyback configuration?
Now this welder is dirt cheap and not worth fixing really, but i wanted to try for my own curiosity.
But now i would like you guys to educate me as to why this doesn’t work.
What am I missing?
Thanks in advance… and go easy on me.
