Unknown tig

[Stepper]

Ni guys Newby here with a problem.
My son bought a tig as a spare at auction, so looking for some info.
Doesn't appear to work and He's asked me to look at it, ( I had a 100% repair record up to now, though that was only 3!).
The unit is BW BLACKWELD model X166.
It seems to start up ok with display running through a short diagnostic displaying amps?. Display then goes to 3 bars - - - and the temp LED flashes, no doubt sensing an error. Temp sensor is in fact ok, so guess its a fault condition.
Only + and - are connected, but no output, any ideas?.
Thanks in anticipation.
Tony.

 

[Stepper]

No response from you guys, but here's the answer. Problem was a transient voltage suppressor, which had gone s/c. Should have it working in a couple of days, cost about 50 pence.
Tony.

 

[malcolm]

Thanks for getting back with the solution. It'll be helpful for the next person with a similar problem.

I wouldn't have had a clue - how did you diagnose the fault?

 

[Stepper]

Because the display etc was responding ok, I surmised that the controlling logic must be working. Also surmised that the unit shut down when it tried to produce hi current DC.
Removed and tested output dides out of circuit and they all looked ok. Removed the heatsink which thay attach to and found 2 limiting diodes hidden under, one was s/c destroying all o/p. No doubt the sensor circuit registered this and shut down the unit.