Thanks for your reply guys. Apologies for my very late reply. I just couldn’t get around to dealing with this with one thing and another.
Eddie49, thanks for confirming the details in the operation of the circuit and of the short I was measuring. And for offering to have a look at it. So Much appreciated.
I continued by removing all the transistors from the circuit and testing them all individually on my transistor tester and found v23 2N3019 to be at fault. I thought I had checked this on my multimeter on diode setting but I guess I overlooked the fact that two pins where open. I ordered a replacement and replaced it and tested it in the welder. All now working 100%. Im delighted.
Again thanks to all who took time to reply.
Just in time for Christmas well done!