Broken welder- advice needed

[bigspanna]

I have a Magnum automig 150 turbo which was working great until it started blowing fuses.On turning it on the fan works as normal,press the trigger and the wire feeder works for about 15 seconds then blows the fuse in the plug.This is without striking an arc.I suspect the wire feed control unit,but this has a small fuse in it which is ok.As you can probably tell I know nothing about how these work or how to test them.Any ideas on finding the fault would be greatly appreciated {in simple language please for a simple bloke}

Thanks

Bigspanna

 

[MigTig]

Whip the case off, and check the PCB (printed circuit board) as I think you may have a short circuit somewhere. If theres been a fault of larger scale, you will usually see visible damage and black soot fouling of the damaged parts.

If the machine has been used for a good amount, it may be at the end of its service life otherwise..

 

[shenion]

The wire feed and PCB could probably never draw enough power to blow the fuse. Sounds like either a short in the transformer or the diode bridge going bad.

 

[weldequip]

I have a Magnum automig 150 turbo which was working great until it started blowing fuses.On turning it on the fan works as normal,press the trigger and the wire feeder works for about 15 seconds then blows the fuse in the plug.This is without striking an arc.I suspect the wire feed control unit,but this has a small fuse in it which is ok.As you can probably tell I know nothing about how these work or how to test them.Any ideas on finding the fault would be greatly appreciated {in simple language please for a simple bloke}

Faulty Rectifier (aluminium plates with diodes in).
weldequip

 

[bigspanna]

Are these rectifiers repairable,or do I just replace it,or does the cost involved
mean its a scrap welder.Seems a shame to scrap it as it used to work really well but it is about 10 years old
Also is there a check I could to to make sure to make sure the rectifier is the problem

Many thanks

Bigspanna

 

[shenion]

You can test the rectifier diodes with an ohmmeter. Each diode should be open one direction and conduct some in the other.

Sounds like one or more is shorted.

 

[Drains]

I believe from other posts that you need to disconnect the rectifier unit completely before testing it or else you'll get false readings. Weldequip may be able to sort spares.

 

[andychud]

I believe from other posts that you need to disconnect the rectifier unit completely before testing it or else you'll get false readings. Weldequip may be able to sort spares.

Absolutely correct. You need to disconnect each one and test them individually. You can test them with an Ohmeter, but a proper diode test is best. You should get no volt drop in the reverse bias direction and about 0.6volt (or more for high-current power diodes) drop in the forward bias direction. Most multimeters have a diode test facility and are available on eBay or Maplin (http://www.maplin.co.uk/Module.aspx?ModuleNo=97045&C=Maplin&U=SearchTop&T=MULTIMETER&doy=3m6) really cheap. These may not be the best quality in the world but are fine for the occasional user.... very handy to have in your toolbox. If you decide to test/repair and need some assistance, please let me know - I'd be happy to help. Farnell have a large selection of diodes and may have suitable replacements if they are found to be faulty.