Help with a sip migmate 120

[Mordo]

Hi, I have a Sip migmate 120, which up untill about an hour ago worked perfectly, came in for a cuppa and when I went back outside, the welder blew the fuse in the plug, replaced that - picked up the torch again and pop, the new fuse went. I thought it might be the feed motor because it sounded like it was stalling, took the motor off only to find it looks and smells ok, while I had the sides off I noticed that the transformer was warm, really warm, bear in mind i'd not used it for at least an hour while I was drinking my tea. Every time I replace the fuse, it blows within 5 - 6 seconds of pulling the trigger, it sounds like its 'struggling' then it blows the fuse, any ideas what I need to do to get it working again? I need to finish the welding on my truck to get it in for a retest asap. Any helpful ideas would be greatly appreciated.

Mordo

 

[R Kraft]

Most likely.
Either the transformer is having a problem or you have a bad diode.
Robert

 

[malcolm]

It's well worth giving the welder a good brush and vacuum inside, then a good blow out with an airline. It's possible something is conducting electricity between the wrong places.

Failing that, the later SIPs have a problem where the thick power cable to the torch can short against the casing. Well worth a good look in that area.

A transformer fault is possible given it was heating up, but such faults are rare, hence the really long guarantees offered on transformers. Rectifier diode is a possibility, but I would have expected the fuse to blow instantly (do you have an RCD on the supply circuit?).

 

[Mordo]

Thanks for the prompt replys.

No there is no RCD on the circuit.

It blows the fuse withing a second or so of pulling the trigger.

Now going to blow it out with the air line. will post results shortly, if it is the transformer is the machine a right off or would it be worth repairing ?

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Ok so i took it into my workshop and blew it thru woth the airline, replaced the fuse and it blew that, only this time I noticed that the 12v relay on the pcb is shorting out, it was sparking. Is it an easy fix or do I need it done by a pro?

 

[R Kraft]

Large sparks from the relay, could just be caused by the drawing of a lot of amps.
Look at the lead wires, if they look ok you might try unhooking the leads from the output diodes.
If it still blows the fuse with the transformer output leads unloaded, it would be the transformer.
Usually a transformer failure is not worth repairing.
Robert