Wolf MIG 140X - Lost 99% of welding power

[SplatterMaster]

Hi Folks,

Had my little yellow "Wolf MIG 140X" for a few years, always used with gas, gone through a few large reals of wire and 2 hobbyweld bottles on various hobby projects.

All was well until the gas valve broke in the torch (always on), failing to find just a replacement valve, I went to replace the whole torch assembly. I opened the welder up took a peak and decided it would be quicker to just swap the valve across inside the torches instead.

I put the covers back on, excitedly clamp the earth to a bit of scrap metal... click settings to my normal preferences for such a thickness... pull the trigger and nothing but a few feeble sparks followed by blown fuse. :-(

the torches where near identical in design, everything done up tight, the coiled wire outer liner bumped up nicely into the back of the tip.

I have pulled the covers back off and had a look for anything obvious I might have disturbed (I literally did just pull the covers off and decide narrr), but can't see anything.

internet reading pointed to shorts or blown diodes in the rectifier so I put a multimeter across the 4 paths through the rectifier (8 diodes in 4 parallel pairs), resistance the same for all 4 routes and current only allowed to flow in one direction through each so without any specs to go off seams healthy?!

what do I do next?
anyone got a link to Wolf schematics?
or general fault finding guides?

any pointer gratefully received!

 

[Hutcho]

Put some pictures off the valves so we can see what is what buddy

 

[SplatterMaster]

will do, got a day off tomorrow :-)

 

[eddie49]

When testing the rectifier you need to set the meter to the Diode Test range ( indicated by a diode symbol ). When conducting, diodes will show "400 to "700" , or 0.4 to 0.7, and in reverse "OL" or "1."
The spool of MIG wire, the wirefeed roller and motor assembly, and the internal end of the torch are all "live". Maybe some part of the new torch is making contact with the case of the welder?
There is a circuit diagram for the Wolf MIG in post #3 of this earlier thread:

WOLF WELD 140 NO WIRE FEED!!!!

Hi all! was using my welder yesterday and all of a sudden the wire feed stopped! I’ve hooked up the motor to a battery and it works with a 12v feed but when I try it with the machine wires there isn’t even a 1v feed. You can hear the relay click but no wire movement!

www.mig-welding.co.uk

 

[SplatterMaster]

When testing the rectifier you need to set the meter to the Diode Test range ( indicated by a diode symbol ). When conducting, diodes will show "400 to "700" , or 0.4 to 0.7, and in reverse "OL" or "1."
The spool of MIG wire, the wirefeed roller and motor assembly, and the internal end of the torch are all "live". Maybe some part of the new torch is making contact with the case of the welder?
There is a circuit diagram for the Wolf MIG in post #3 of this earlier thread:

WOLF WELD 140 NO WIRE FEED!!!!

Hi all! was using my welder yesterday and all of a sudden the wire feed stopped! I’ve hooked up the motor to a battery and it works with a 12v feed but when I try it with the machine wires there isn’t even a 1v feed. You can hear the relay click but no wire movement!

www.mig-welding.co.uk

Values in forward and reverse:
485,1
485,1
466,1
466,1

Time for a cup of tea and short hunting...

 

[SplatterMaster]

Reference pics for welder identity confirmation

 

[SplatterMaster]

I can't find any shorts of the positive to ground anywhere (I was so hoping it was just the pliers and crap I normally leave in the bottom of the wire real chamber...)

Have wiggled every connection.

And have now tried every combination of torch components I can think of... :-(

Begining to think I must have broken something (/ disturbed a broken thing juuuuust hanging in there) moving the welder from its corner of the shed to work on it.

Time to crawl through the wiring diagram!

 

[a111r]

Are you getting any voltage at all between the tip and work return, over the 6 voltage settings?

The next thing I'd be checking after this is the transformer's primary winding resistance at each switch position.

 

[SplatterMaster]

I'm getting some voltage at the tip, just barely enough to melt the mig wire.

Tracing the switch wires to the transformer taps was proving tricky so I've labelled Vs switch outlet position and unwired to test

From start of primary winding (230v) to:
>Tap 1 - 1 ohm
>Tap 2 - 1.4 ohm
>Tap 3 - 2.7 ohm
>Tap 4 - 1.5 ohm

Secondary winding
>Smaller than my meter can measure ohm

In/out on filter(rectifyer -ve > filter > ground clamp wire)
>Smaller than my meter can measure ohm

 

[SplatterMaster]

I've also taken the filter and transformer out to get a better look for signs of burning etc, nothing, all looked fine.

Probably worth noting the wire feed, fan etc all work as normal.

The power light is on (illuminated/light)
The overload light is off (un-illuminated/dark)

 

[Hutcho]

At the back of the rectifier - they is one of the cables that corrodes - pos and negative , just check them too

 

[a111r]

I measure the primary taps by substituting the mains into the rotary switch with the meter leads, then measure Ohms at each switch position.

Another easy test (for elimination) is to bypass the thermal switch.

 

[SplatterMaster]

I measure the primary taps by substituting the mains into the rotary switch with the meter leads, then measure Ohms at each switch position.

Another easy test (for elimination) is to bypass the thermal switch.

Haha, that would have been a far easier method... I'm clearly not thinking all that straight today.

 

[a111r]

Haha, that would have been a far easier method... I'm clearly not thinking all that straight today.

Well it does avoid trying to interpret schematics (like this, that fog my brain) and also takes care of any taps that are combined.

 

[eddie49]

Very low voltage at the torch tip and barely melting the MIG wire indicates an open-circuit diode, but blowing input fuses/breakers tripping would be a short-circuit diode...

What AC voltage do you get across the transformer secondary, and DC voltage at the torch tip, at each of the 6 positions of the rotary switch?

If you temporarily disconnect one of the transformer secondary wires from the input to the rectifier, does the fuse still blow?

As Hutcho said, it would be worth inspecting the positive and negative terminal posts/feed-throughs at the Gas/No-Gas swap location, to confirm that they are clean and tight on both sides and insulated from the bulkhead.

 

[Hutcho]

Looking at the trigger switch also , not sure if that’s upside down - looks like they is a notch in the switch that goes to the top of where it sits , as you have one terminal under the gas valve - maybe that shorted and caused the problem .

 

[SplatterMaster]

At the back of the rectifier - they is one of the cables that corrodes - pos and negative , just check them too

Taken it off this evening, no corrosion or signs of distress

 

[SplatterMaster]

Looking at the trigger switch also , not sure if that’s upside down - looks like they is a notch in the switch that goes to the top of where it sits , as you have one terminal under the gas valve - maybe that shorted and caused the problem .

Looked iffy to me too but it's the same way in both torch's and I added insulation tape as a anti short security measure.

 

[SplatterMaster]

I measure the primary taps by substituting the mains into the rotary switch with the meter leads, then measure Ohms at each switch position.

Another easy test (for elimination) is to bypass the thermal switch.

Thermal switch bypassed, no difference :-(

 

[SplatterMaster]

Very low voltage at the torch tip and barely melting the MIG wire indicates an open-circuit diode, but blowing input fuses/breakers tripping would be a short-circuit diode...

What AC voltage do you get across the transformer secondary, and DC voltage at the torch tip, at each of the 6 positions of the rotary switch?

If you temporarily disconnect one of the transformer secondary wires from the input to the rectifier, does the fuse still blow?

As Hutcho said, it would be worth inspecting the positive and negative terminal posts/feed-throughs at the Gas/No-Gas swap location, to confirm that they are clean and tight on both sides and insulated from the bulkhead.