Mig welder up the spout. Help!

[Seadog]

More likely it's a thermister

More likely to be a Varistor Matt (voltage dependent resistor). It limits voltage spikes.

 

[MattH]

More likely to be a Varistor Matt (voltage dependent resistor). It limits voltage spikes.

Yes spot on, that's what I meant. I was looking at the word thermistor when I typed it thinking that doesn't look right.

Varistor.

 

[the snooper]

Chunkolini read the value from the varistor lollipop order one and fit it if that it where the spark came from

 

[chunkolini]

There does look to be some kind of "combustion event" taken place.
Am i ok using it before replacing the ex diode. Are they easy to source

 

[WorkshopChris]

Chunkolini read the value from the varistor lollipop order one and fit it if that it where the spark came from

Am hoping for his sake it is just a failed MOV but not to sure, combined with the posible burn marks in line with the end of a diode location i have a feeling its at least 1 diode shot.

 

[WorkshopChris]

Am i ok using it before replacing the ex diode. Are they easy to source

Just seen this we must of posted at same time, depending on how many diodes are fitted in your rectifier you may be ok for a while on low settings, but if there is only 1 fitted then or more than 1 gone your welding will be poor as you will be working with half rectified dc so lots of ripple. Mig doesn't like ac.

Some are bolt in most of that size are press fit. you may need to disassemble the whole rectifier to replace, i would try to replace them as a matched set.
You have a few options depending on specification.

Complete rectifier assemblies are also available maybe speak to someone like Jim Davey once you have had a chance to asses any damage.

 

[Jim Davey]

Pretty straightforward to replace the rectifier, just need the physical dimensions really.

 

[the snooper]

just read workshop chris's post yeah looks something amiss with the rectifier

 

[God mode restorations]

Wish I could get mine fixed. It's on its way to some part of the world to oerlikon hq....great

 

[normspanners]

Working fine now.
Maybe the workshop monkey telling me to clean my welder out now and again.
Thanks for speedy attention.

Surely wouldnt be working FINE now, if one section of rectifier had blown, it would give a rough old weld on partial ac ?? coz a diode isnt going to repair itself.
whereas a crowbar resistor would eventually be zapped open circuit, and is there to save possible damage to caps etc.

 

[chunkolini]

it was working fine, and lasted two days which was a relief as I had a course last Monday and Tuesday.
At the end of the second day it failed again; just as my student was doing his very last weld.

I took it to an electrician up the road and £140 for a 230amp rectifier fitted and delivered back to it is fine again. he showed the remains of the old one. the diode had exploded quite nicely. Al sorted out and back in action. A relief as I need it.

 

[the snooper]

it was working fine, and lasted two days which was a relief as I had a course last Monday and Tuesday.
At the end of the second day it failed again; just as my student was doing his very last weld.

I took it to an electrician up the road and £140 for a 230amp rectifier fitted and delivered back to it is fine again. he showed the remains of the old one. the diode had exploded quite nicely. Al sorted out and back in action. A relief as I need it.

hope you kept the old rectifier to add into a project