BOC Autolynx electronic

[Ric Walker]

I have a BOC Autolynx electronic which works really well except if I accidentally earth the item I’m welding, when it blows a fuse after a few seconds of poor welds. It always did this but previously after a while it would behave properly, maybe after it warms up?. It only gets occasional use, so maybe damp gets in, there’s no visible wetness inside but there’s clearly a problem. I took the cover off, i sort of understand the general ideas and could replace whatever is wrong, but no ideas on what’s wrong without circuit diagram. Any ideas, anyone? Much appreciated whatever comes back…… it’s too good to get rid of!

 

[jo1010]

Not sure what you mean by "accidentally earth"....isn't your ground cable earthing the work? Have you checked ground cable / clamp for rusted connections.
Does it happen on all power settings?
Which autolynx model is it?

 

[mike 109444]

like one of these ?

 

[eddie49]

Hello, and welcome to the Forum.

Normally both sides of the low-voltage high-current output of a welder should be isolated from the welder chassis, from mains Earth, and from all the lines of the incoming AC power source, i.e. it is a fully-floating output. This separation applies to a traditional transformer-based welder and to a modern inverter, and to all types of welder - Arc, MIG, TIG, AC, DC. It is achieved through the use of dual-wound transformers.

The fault you have described indicates leakage from the AC mains supply to the welder's output.
Have you checked the integrity of the machine's own Earth circuit? I.e. chassis, yellow/green wire, ground pin in 13A plug.
Do you normally power the welder from a source that has earth leakage protection ( RCD or RCBO )? If not, check if plugging in to a protected supply, powering on, and pressing the trigger, without welding, causes the breaker to trip.
Check for stray AC voltage on both the torch tip and the work clamp, with a voltmeter to Earth or a neon test screwdriver.

[ Calling the work return cable and workpiece clamp the "Earth lead" or the "Ground cable" is erroneous. It has no electrical connection to actual AC mains earth, nor to the soil of Planet Earth.]