Have got a dead thermal arc 202 AC/DC Tig that is dead no display and fan doesn't run when turned on. Has anyone got any service information so I can check the board voltages in different places. Thanks
Is the machine still under warranty? If so, return it to the supplier and ask for a replacement, a refund, or repair.
I'm afraid that amateur repair of an inverter welder is very difficult, if not impossible. The problem issues include complex circuitry, no circuit diagram, high voltages inside, high operating frequency, unmarked, unknown, unobtainable components, surface-mount construction, and high component density.
You could start with a visual internal inspection. Power off and disconnect the input power cable. Wait for any voltages held in charged capacitors to decay, then remove the casing. Look for loose or badly-seated plugs on the multi-cable board-to-board harnesses and push-on tags, burnt components, loose or corroded connections, dry solder joints, and loose screws or bolts on the high-current wires and busbars.
The power input may go through a filter circuit of capacitors and inductors to limit back-interference to the AC mains. This could be potted in a metal can. There will probably be a double-pole main switch, and then it is on to one or more ( paralleled ) bridge rectifiers. The DC output is fed to a bank of electrolytic capacitors, probably 500 to 2000 uF. There may be a soft-start circuit to reduce the initial power-on surge when the capacitors first charge. This may be a pre-charge resistor that gets bypassed by a relay after a short delay.
On the capacitors there will be 325v DC, and this DC bus runs all of the machine. In the primary inverter, it will be chopped to high-frequency AC by IGBTs or multiple parallel MOSFETs, under the control of a micro controller or a microprocessor.