Lotos 520d plasma part not working, arc works great

It does say it is primarily a TIG welder. My guess is the the sticks are too heavy gauge for it. Did you get a manual with it?

https://www.google.com/search?q=Powcon+300ST

https://www.google.com/search?q=Powcon+300ST+manual

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MIG welding is also called Metal inert gas welding, gas metal arc (GMAW) welding. MIG welding uses an arc of electricity that creates a short circuit amidst a constant anode and a cathode. The short circuit produces heat and a non-reactive gas. This melts metal, enabling it to be mixed together. After the heat is removed, the metal cools down and then solidifies, creating new fused metal. MIG wire is used in MIG welding. Tungsten inert gas (TIG) welding utilizes a non-consumable tungsten electrode that produces the electric arc for the weld. Unlike MIG welding, TIG welding does not require additional metal to be added.

Arc welding is any welding process that uses electricity, which includes MIG, TIG, and SMAW. SMAW Shielded metal arc welding is most commonly referred to as stick arc welding. In SMAW welding the stick electrode contains a flux that keeps the atmosphere from contacting and contaminating molten metal. It is a good choice for welding thicker metals. It is a manual process, that is hard to get a hand of. yet once done. MIG welding is a semi-automated process that is a much better option to use on thinner metals. It is easier to get hang of than SMAW welding. A welding MIG wire is used in the MIG welding process. TIG welding is the hardest as compared to SMAW & MIG welding. It is capable of producing an autogenis weld which is one does not use any filler. These are some differences in arc welding processes.

normal
the light emitted from a tig arc is many more times intense that normal arc light so you will need much darker lens to view the welding process through
if you are using automatic darkening lens thenhave it checked that it is suitable for tig welding as the dark settings may not be low enough or adjust the settings on the helment to lowest possible

check fuse, or other loose connection

Your polarity needs to be switched for Tig operation. In other words, the electrode will be negative. Make sure you use the proper gas for Tig, usually Argon.

the spark that you see when you touch work peice is high frequency,recheck connections like good ground (tight and clean)on the unit and work peice.no ground no fire.

remove the fan from the circuit and try it then, does it weld ok with the fan removed?

TIG stands for Tungsten Inert Gas welding. Also called GTAW (Gas Tungsten Arc Welding) and Heliarc® which was Linde's trade name for the TIG process when it was introduced many years ago. The arc is started with a tungsten electrode shielded by inert gas and filler rod is fed into the weld puddle separately. A slower process than MIG, it produces a more precise weld and can be used at lower amperages for thinner metal and can be used on exotic metals. TIG does require quite a bit more time than MIG to learn. It is similar in technique to gas welding.