Mighty Midget welder

[mightymidget]

Can anyone help me I have a Mighty Midget ac welder powered by a 2 cyl diesel Lister but I don't get get enough output to weld, it need exciting I guess but I don't know how to do it on ac.

 

[zzr1200]

I fairly sure they are a self exciting alternator generator, check to see if your selection switches have continuity between terminals and the wiring connections are tight.







If the above are OK then, sorry to be the baring of bad news.......but


















































I think the simple answer is, the alternator is scrap.

 

[mightymidget]

Hi sorry late reply as I was working on the welder,it has been stood a very long time,I just got some power to the gen side also a little power to the amp side but cannot weld as its low amps thank you for your reply

 

[HughF]

These are permanent magnet alternators with rotating magnets and fixed windings. If the rotor has ever been removed, the alternator is scrap.

could be a wiring issue, perhaps the rotary selector has gone bad. How does everything look inside the top cover?

Is this ac2 powered or the bigger version?

 

[mightymidget]

The welder did not weld when I started it after been stood some years so I opened the welder and cleaned it all looks good inside the top and inside the welder

 

[mightymidget]

its an AC welder with a 110v gen side

 

[HughF]

I'm well aware of what it is, I have one, I asked what engine it has because it might be the 250 amp, or might be the 300 amp one, and the wiring might be different.

 

[mightymidget]

its the big 2cyl Lister not the small one

 

[HughF]

measured the ocv yet?

 

[mightymidget]

on the switch the high output is 270-300

 

[mightymidget]

What is the ovc please

 

[mightymidget]

ocv

 

[HughF]

Open circuit voltage. Fire it up, stick a voltmeter across the welding outputs with the meter set on ac volts, you should see around 70-75 volts with the lister at 3000 rpm.

 

[mightymidget]

is this the voltage emanating from the arc welding torch or gun when current is not flowing

 

[HughF]

Yep

 

[mightymidget]

Ok I will try and get the reading thank you

 

[HughF]

Whereabouts are you in the UK?

 

[mightymidget]

its 17.5 v

 

[mightymidget]

I'm in Leeds

 

[HughF]

There's your problem.... Does the 110v side work properly? Should run a 2kw load (well, mine does)...