find the century factory service manual.. hopefully online..
without it youre flying blind
begin diagnostics
1) Discharge the capacitors so it is safe to be inside the machine... if you dont you can receive a hi voltage shock that WILL kill you... do not skip this step... DO NOT SKIP THIS STEP.. if you dont know how to do it you shouldnt be in there
2)Methodically begin checking all connections, obviously there is power to the machine... but there may not be power to the transformer or capacitors
3) Next it will be the silcon controlled rectifier and the diodes
4) Transformer test
thats pretty much a simplistic diagnostic... the service manual will have the trouble shooting section and wiring diagram which are both invaluable
Lastly.. welder repair station.. century is an off brand and parts are harder to get... but they are still around...
IIRC that has a tweeko gun on it ..right? make sure the gun connections are also good.. I suspect they are because you are getting 110v to it...
it was my first welder...then I went red for life
btw Lincoln aquired Century in 2003 and now they are begining to look like lincolns... but they have cheaper components inside.. I looked around lincolns site to see if I could find any shop manauls or anything pertinent about them,,,, I couldnt.. google didnt help much either... but give it a shot
sorry I couldnt be more help