Welder tig repair

[Norm]

Have Tig welder could anyone help please it turns on that try to start to weld it only goes for very short duration while pregas flow and sparks to metal , then stops and doesn’t weld have checked all the torch wiring and have continuity , but will not kick into action 

[jpanhalt]

Not much to go on.  Assuming it has HF for starting, it sounds like that is working, but the main power is either not being enabled or not working.

[Zenith]

Which brand? What sort of TIG welder? Basic or a flashy one which can weld aluminium?

I assume it's inverter based rather than a traditional design. If so they are complicated beasts and circuit diagrams and service notes are often not easy to find. If you can find the service manual, often it's clear the maker was thinking in terms of board swaps rather than component level repair.

Some of the cheap Chinese ones look more like a prototype than something that should be in production.

[Psi]

How long in seconds does it work before stopping?

If less than a second it could be a current sense issue.

If a few minutes then it could be overtemp problem.

have you tried other modes, does your TIG support MMA/Stick welding?  Does that do the same thing?

[coppercone2]

yeah mine is still broken after 1 year, its 20 miles of bad road to fix one of those.

Replaced tons of burned out parts but it still blows some HV fet in a cascode? thingy on power up. The problem kept relocating. After enough tries maybe....

hours and parts wise, I could have bought a working used one.

If you had full schematics made by the manufacturer. The manufacturer test procedure is very useless. The generally high voltages make trouble shooting it unpleasant/time consuming, and its usually built really unfriendly. People know which boards are problem boards so expect the boards that don't normally break go for 400% (four hundred+) cheaper then the ones that are trouble makers.

FYI the deal with the inverter machine is if you run it from a split phase, you are trouble shooting a 800V very low impedance rail. That's like working on the subway. Be very very careful if you try this and never probe the beat to a pulp power components while its turned on and all that annoying stuff.

I say that you should pass this 'opportunity'

[Norm]

Thankyou guys for your help appreciated, yes it’s ac,dc, alloy welder  no it does not work on stick either yes it starts to go, but does not go to full power to weld , and just stops . It just sparks for as long as pregas flow ,I have to now get a little MOSFET for it cause I cleaned it with electrical cleaning fluid and it mustn’t have dried out properly cause when I flicked it on to check it one went bang and blew chip out of it . I had a person at a welding repair shop tell me I can’t just put one it I have to put that particular row in or it will blow again cause they won’t be even in power , sounds to me he is talking rubbish , 

Not much to go on.  Assuming it has HF for starting, it sounds like that is working, but the main power is either not being enabled or not working.

How long in seconds does it work before stopping?

If less than a second it could be a current sense issue.

If a few minutes then it could be overtemp problem.

have you tried other modes, does your TIG support MMA/Stick welding?  Does that do the same thing?

yeah mine is still broken after 1 year, its 20 miles of bad road to fix one of those.

Replaced tons of burned out parts but it still blows some HV fet in a cascode? thingy on power up. The problem kept relocating. After enough tries maybe....

hours and parts wise, I could have bought a working used one.

If you had full schematics made by the manufacturer. The manufacturer test procedure is very useless. The generally high voltages make trouble shooting it unpleasant/time consuming, and its usually built really unfriendly. People know which boards are problem boards so expect the boards that don't normally break go for 400% (four hundred+) cheaper then the ones that are trouble makers.

FYI the deal with the inverter machine is if you run it from a split phase, you are trouble shooting a 800V very low impedance rail. That's like working on the subway. Be very very careful if you try this and never probe the beat to a pulp power components while its turned on and all that annoying stuff.

I say that you should pass this 'opportunity'

Not much to go on.  Assuming it has HF for starting, it sounds like that is working, but the main power is either not being enabled or not working.

Which brand? What sort of TIG welder? Basic or a flashy one which can weld aluminium?

I assume it's inverter based rather than a traditional design. If so they are complicated beasts and circuit diagrams and service notes are often not easy to find. If you can find the service manual, often it's clear the maker was thinking in terms of board swaps rather than component level repair.

Some of the cheap Chinese ones look more like a prototype than something that should be in production.

yeah mine is still broken after 1 year, its 20 miles of bad road to fix one of those.

Replaced tons of burned out parts but it still blows some HV fet in a cascode? thingy on power up. The problem kept relocating. After enough tries maybe....

hours and parts wise, I could have bought a working used one.

If you had full schematics made by the manufacturer. The manufacturer test procedure is very useless. The generally high voltages make trouble shooting it unpleasant/time consuming, and its usually built really unfriendly. People know which boards are problem boards so expect the boards that don't normally break go for 400% (four hundred+) cheaper then the ones that are trouble makers.

FYI the deal with the inverter machine is if you run it from a split phase, you are trouble shooting a 800V very low impedance rail. That's like working on the subway. Be very very careful if you try this and never probe the beat to a pulp power components while its turned on and all that annoying stuff.

I say that you should pass this 'opportunity'

[jpanhalt]

Thankyou guys for your help appreciated, yes it’s ac,dc, alloy welder  no it does not work on stick either yes it starts to go, but does not go to full power to weld , and just stops . It just sparks for as long as pregas flow ,I have to now get a little MOSFET for it cause I cleaned it with electrical cleaning fluid and it mustn’t have dried out properly cause when I flicked it on to check it one went bang and blew chip out of it . I had a person at a welding repair shop tell me I can’t just put one it I have to put that particular row in or it will blow again cause they won’t be even in power , sounds to me he is talking rubbish ,

Actually, you are the one talking rubbish.  Since you continue to fail to provide any useful information despite every respondent asking for it, let me make one last attempt.

1) There is a good chance the "blown" mosfet was in parallel with other mosfets.  In that case they need to be matched.  Read about load balancing.
2) If the mosfet was single device, there are 4 types, two of which are common.  You must have the right type, and  its specifications must match what it is expected to do.
3) Cleaning ordinarily doesn't do damage, unless  you cleaned it incorrectly.  In any event, given what you say happened, even if you replace that mosfet with an identical device the problem still exists, and it will not work or may blow again.
4) Take your welder to a competent repair station.  So far, based on just your two posts, it does not appear you have the competency to do it yourself.   

[Zenith]

Norm, I haven't got the impression you are heavily into electronics repair. These things are complicated and twitchy and fixing them is something of a specialism. I have fixed a couple of MMA inverters, but an AC/DC TIG welder is a different level of complexity. They are potentially lethal, with about 1,500µF of capacitors charged to about 330V, which could remain for a long time under fault conditions. As I said, the makers usually recommend board swaps, that is when the idea of fixing them, rather than chucking them, has occurred at all.

I don't like to be a wet blanket, but I suggest you don't mess with this. Sell it on ebay for spares or repairs (they fetch a surprising amount) or get a specialist welding gear repairer to fix it - the cost may be eye watering.