No Arc!! Please advise

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I have a nice Hobart Mega arc 400-dd it is a sweet running air diesel  but for some reason it will not arc. The man I got it from use to jump from the 12 volt battery to a switch to get it to start working and I am assuming maybe it was the exciter but I am far from an electrician!! I am very mechanical so I just need to work down to the failing switch any help would be great and appreciated!! Thank you kindly
Reply:First you should have posted this in the Hobart room.Second try to find the bridge rectifier block in the exciter circuit. Make sure it is not open or shorted. If this is a real old welder you may have to flash the fields every time you start it up.  An auto flashing system uses a relay and a blocking diode to apply battery voltage to the brushes when the motor is being cranked. The diode keeps the higher excitation voltage from damaging the battery. Relay is wired it the crank circuit. Contacts are open in stop and run. only closed in start.
Reply:K so do you have any suggestions on a Hobart site to try? Thanks
Reply:I'm pretty sure ccawgc meant posting in the Hobart section here but you could also try the Hobart website forum over there.http://www.hobartwelders.com/weldtalk/Is there a wiring diagram on the inside of one of the enclosure panels?  If there is, can you post a clear photo or photos of it?MM200 w/Spoolmatic 1Syncrowave 180SDBobcat 225G Plus - LP/NGMUTT Suitcase WirefeederWC-1S/Spoolmatic 1HF-251D-1PakMaster 100XL '68 Red Face Code #6633 projectStar Jet 21-110Save Second Base!