I purchased a huge welder a few months back brought it home and know it won't adjust heat. I've checked pot and replaced I sent the PCB to be checked out but not thinking that will be the problem. I can seen the electrical print on the machine if it will help.im blowing a 20 amp fuse that is inside the welder,which I think means I've got power going to ground.if anyone can help it would be greatly appreciated as no one want to work on it because it's old.thanks in advance.

 

F1, F2 are on pg 16, feeding the thyristors Scr1,2. So what are they feeding?

 

F1 is blowing it goes to the cti which goes to the control the bottom of the electrical print my DC voltage never changes when you adjust the pot it say to check scr but I don't know how

 

To check the thyristor, remove the wires from the Anode and Cathode, measure the resistance on diode test across the Anode and Cathode both ways it should read open circuit, .

Then test the the thyristor with the Anode positive lead and temporarily short the gate to anode, negative lead on cathode, it should conduct short circuit or low ohms.