Selco genesis 145 inverter welder MMA issues

[epsilon]

Hi,

I am new to this forum, I am trying to fix mu inverter welder. It is Selco welder, model genesis 145A with 2 modes: TIG and MMA. I've always been using it in MMA mode. It worked perfectly. Suddenly, it just started loosing power. When I start to weld, it makes the arc, melts the electrode, but very slowly, not able to penetrate metal, just drips some drops on the surface. Arc stays stable with no power. I've found the service manual, there are couple of diagnosis LEDs inside the welder which tell about the voltages - they are all OK. Checked potentiometer for regulating power, connections. No signs of burning anything but the little zener diode near to relay for soft start. I checked it, it is OK, just a little black from heating. I've found somewhere also that relay needs to be checked visually 5 seconds after turning on the master switch - so it works also fine. Before desoldering mosfets, diodes, capacitors and checking them, did anyone have a similar issue?

Thanks a lot for any help/opinion.
Regards.

 

[Wendelspanswick]

Have you changed from DC- to DC+ or is it the other way round, can never remember.

 

[epsilon]

Hi, do you mean cables for earth and electrode? I think they can't fit in the wrong way.

 

[wheresmejumper]

Have you tried it on tig?

 

[epsilon]

Yes, just tried but with common MMA electrode (because I don't have a TIG torch), it produces an arc as (i think) it should be for TIG, but doesn't weld (as far as I know TIG has a limit of 10A). I thought that little switch which switches from TIG to MMA could be causing the issues, but it works good (checked it), and also there's different sound when I switch it from TIG to MMA and conversely.

 

[wheresmejumper]

I mentioned it as stuff like hot start and arc force and anti stick are disabled in tig.if it was one of these playing up which looks unlikely now then tig would work okay.it would need a tig torch and argon to verify,but I wouldn't be buying them just to check

 

[epsilon]

I understand, but anyway I don't have it at the moment I'll try to do more research and diagnosis.