Welding Tips and Tricks

Hi, I am new to the forum and based in the UK. My machine is a Danish single phase Migatronic, type MTE220. I am hoping there may be some electrical experts who can advise on an issue my machine has since a failure was supposedly attended to.

I am trying to fix my Migatronic single phase 220 amp TIG welder. I had the reactor (choke) go short circuit internally, between windings. I have had it professionally rewound. I now have an issue that unless I disable the HF the digital current display goes wild, and there is random or no control of welding current, on both AC and DC settings. Would you expect the HF to run all the time the torch trigger is pulled, on both DC and AC? Or to shut down once the arc is established? Would you expect it to run on both AC and DC settings?

If I deactivate the HF generator by pulling the fuse to the HF transformer primary, the current display is 100% stable. By a fiddly process of scratch starting, once I get an arc, the current control in both AC and DC modes is functional and seemingly OK. Before the choke (reactor) shorted, the machine had zero issues, so I had no cause to consider when and if the HF should and did run. I never saw an unstable current display though, either with the torch trigger pulled (which I had to do to see the current setting) and no arc, or with an arc established. So something has changed... thanks. I have schematics for most of the machine and some electronic knowledge, but not much specific to welders...


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Best regards, Chris Wilson.

Welcome, Chris,

I can't help on this one, but I have little doubt someone can.

We have a few here who know machines quite well, and also a few who will dig up the scematics (and can understand them) who will chime in over a few days.

Steve S

If the machine puts out a fancy squarewave in ac, it only needs hf to initiate the arc.just like dc.
if it is a plain old transformer putting out sinewave, then the hf needs to stay on the whole time or the arc will extinguish.
sounds like yours is square. Possibly the hf voltage is leaking out and interfering.i would contact migatronic

Welcome to the forum.

Thanks for the welcomes, and the replies. I have now delved deeper and found only one of the two SCR's in the output is receiving a gate trigger signal. The Schmitt trigger circuitry is not shown on my schematic at all. I may have to just try and work it out from the quite complex double sided PCB layout. I don't think bench powering the board is feasible, so I am lugging test gear to the TIG itself in a different workshop. If by chance anyone has the schematic for a Migatronic MTE series Type 1 control box I would be happy to buy a copy. The output is pseudo square wave, I think the HF is meant to run all the time, but I first need to get both SCR's firing. Thanks all.