Sickly cut 50

[Winston666]

I have a generic cut 50d which does not produce an arc. This started as being a little difficult to start initially but once the arc had been established happily worked all day, however now nothing, the machine switches on and the air solenoid energises but that's it. I have taken the covers off and was expecting to find a loose connector, burnt out resistor or similar but nothing obvious. I was actually impressed with the build quality, all connectors are fixed in place with silicone, heatsinks are large and the wiring is neat and tidy. I was expecting the earth lead to be connected to chassis earth, however this is connected to a terminal marked +ive, with the torch connected to a negative rail. I have tried a brand new torch with no change. Where do I start fault finding?

 

[Mart63]

@skotl knows a lot about these machines.

 

[TryingToWeld]

I had one that wouldn't arc, see Cut 50, No Arc

 

[Winston666]

I had one that wouldn't arc, see Cut 50, No Arc

Thanks, going through the thread.

 

[skotl]

I have a generic cut 50d which does not produce an arc. This started as being a little difficult to start initially but once the arc had been established happily worked all day, however now nothing, the machine switches on and the air solenoid energises but that's it. I have taken the covers off and was expecting to find a loose connector, burnt out resistor or similar but nothing obvious. I was actually impressed with the build quality, all connectors are fixed in place with silicone, heatsinks are large and the wiring is neat and tidy. I was expecting the earth lead to be connected to chassis earth, however this is connected to a terminal marked +ive, with the torch connected to a negative rail. I have tried a brand new torch with no change. Where do I start fault finding?

I'd pay very close attention to the board with the air contacts, as mentioned in the other threads.
If there's no obvious burning then a reasonable next step is to remove a leg from each component one at a time and check each component out of circuit. Seems like 95% of failures tend to be on that board.