get on the net, millerwelds.com with your model and serial number and you should be able to get a schematic in PDF format...the 4 diodes should be available even if not from Miller..there should be a number/letter combination on the side of the diode/rectifier,like "1N4558" or something like that..a lot of times two are the same and the other two have an inverted polarity for ease of manufacture and mounting/wiring.They usually are wired/configured in a 'bridge' formation(like a square)-with AC(~) in on two corners and DC (+/-) out on the other two. They are mounted right in front of the fan on a strip of aluminum as a heatsink..it draws the heat off the diodes.Sometimes they use two diodes and two SCR's to control the output..Lets start in the basement fIrst and work our way thru it..If you have to, its a good idea to replace all 4 diodes as the one that went bad will fatigue the others when it blew up or shorted. Newark.com or Mouser Electronics may have the diodes you need. Get back to me/us with the diode numbers,maybe I can help. By the way the big chunky transformer (4th photo down) coil you said had a measurement of 1ohm is a choke,it's probably OK..they are bombproof.