TIG welder repair. Help identifying

[MattH]

as a few people know I nabbed Stu's Tig welder for spares / repair.
Stuart was under the impression that there was a circuit diagram inside but no such luck.
There is a bit of visible damage to a relay and an adjustable resistor.

Can anyone shed any light on the make of this machine or give me any pointers on circuit diagrams?

 

[HughF]

Can't help with the identification I'm afraid, but when you get it going I'm happy to spare an afternoon showing you the ropes if you want...

 

[eSCHEn]

I've got a TIG that I think is from the same manufacturer Matt - here's a thread on it. The guts and casing do look familiar to me.

There's some internal pics there as well but I can get more if you're desperate for numbers and ratings.

 

[HughF]

I think that is a british machine - I had the exact same gas solenoid in a brit-arc mig I had... Are the threads all metric or imperial? Are the crimp lugs US or British pattern?

 

[MattH]

Cheers for all the replies guys and thanks Hugh for the offer.

eSCHEn, they certainly look to be the same make. The ratings are printed on the back and look very similer to yours.

I haven't checked the threads or anything but I think it is British made. There is an input for 415v and 240v on the back with a switch to select which. Max current draw is 35A on 240v with 150A Tig output. Hopefully it will be fine running off of a 32A supply.

I will swap out the relay and measure the resistance and gauge on the wire on the big resistor and then rewind it with some new.

 

[eSCHEn]

Cheers for all the replies guys and thanks Hugh for the offer.

eSCHEn, they certainly look to be the same make. The ratings are printed on the back and look very similer to yours.

I haven't checked the threads or anything but I think it is British made. There is an input for 415v and 240v on the back with a switch to select which. Max current draw is 35A on 240v with 150A Tig output. Hopefully it will be fine running off of a 32A supply.

I will swap out the relay and measure the resistance and gauge on the wire on the big resistor and then rewind it with some new.

Sounds like you've got it well in hand Matt but if you need anything checking on mine the just ask.

 

[Pete.]

I have four of those resistors but I fear they are wound with lighter gauge wire. If you post the details I'll compare them for you. If one is suitable you can have it.

That arcing looks like it's been shorted on the casing.

 

[MattH]

I have four of those resistors but I fear they are wound with lighter gauge wire. If you post the details I'll compare them for you. If one is suitable you can have it.

That arcing looks like it's been shorted on the casing.

Thanks Pete that very generous of you. I will give them a measure in the morning and post up some details. I hadn't considered it shorting to the case. I will check for tell tales tomorrow.

 

[MattH]

Pete, here a pic of the resistor out of the unit.
I measures 223mm long (the ceramic not including the mounting bolts) and 47.5mm wide (including the windings).
The wire is 1.5mm or 60/1000th inch across.

The connections are made between the two clamps that are closest together so worst case I can move the middle clamp to be the correct distance from the bottom and then flip the resistor end over end and use the good windings left on the other end.

 

[MattH]

There are a number of fuses in the unit that are not correct. On the back there is a switch for changing between 415v and 240v, below this are two fuse holders marked as 1A (I presume to run some of the smaller mains voltage circuitry inside). One holder has a 2A fuse in it and the other has a 5A so presumably it was blowing fuses and someone just put a bigger one in that then lead to the other issues.

There is a 415v - 24v transformer inside that also has a fuse mounted to it on the primary winding, this fuse has broken at the end but not blown.
Strangely this 24v transformer doesn't seem to have any supply from the 240v switch so I don't know where the 24v comes from if using 240v.

 

[MattH]

The relay board also has some problems. The main relay has a burnt contact inside, this relay (I think) feeds the big resistor. I think the relay has arced on closing and has stuck in position, causing current to permanently conduct through the big resistor rather than just at strike up (?).
The board has also had one of the smaller relays replaced poorly in the past, the replacement part was bigger and it has been "bodged" into the board.

I will go through and correct all these issues and replace all the fuses with the correct ratings. Hopefully this will be the extent of the damage.

 

[HughF]

Crepe tape board, oldskool

 

[MattH]

What I don't understand is that all the 24v circuitry is supplied from a big 24v transformer. But this transformer only has a single 415v primary.

How does this work when running from 240v?

 

[Pete.]

One live from 3 phase produces 240v to neutral.

 

[MattH]

The welder has a connector block inside that takes a 240v live and neutral and two phases of 415v. From this block 4 blue cables run up to the voltage selector switch.
Both the supply cables have been removed and the holes blanked if with grommets. Another hole has been added at a later date with a big 3 phase cable feed through to the connector block (the black conductor was left floating!).
I have now removed this cable. The transformer is feed from the selector switch and is marked as 415v. The wires obscure it in the pic but it says 24v-0 and 415v-0.

 

[Pete.]

415 - 0 doesn't make sense. 415v is generated across two phases by virtue of the fact that you have offset waveforms. If you take one of those phases it'll only have 240V from 0 (neutral).

I suspect that the transformer is powered by one phase and neutral and is mis-labeled as 415v, perhaps deliberately. It would work fine on 415 or 240 if that's the case.

EDIT: actually I just noticed something about that 3-phase cable. It has no neutral. If you still have it open it up and see if the three lives are connected to the three lives. It could be they have connected one to a phase, another to neutral and left the black disconnected in the plug.

 

[Pete.]

No luck with my resistors I'm afraid they are much too fine. 0.25mm resistor wire.

 

[MattH]

Brown and blue are each connected to a phase, black is disconnected and neutral isn't used.

 

[MattH]

No luck with my resistors I'm afraid they are much too fine. 0.25mm resistor wire.

Thanks for checking anyway Pete. I think I can get away with using the good end of the current one without rewinding it.

 

[roofman]

Ive got a feeling this is going to turn out to be a good buy...sorry i cant help but goodluck Matt