Microwave not heating - replaced magnetron; now what?
"Don't do that"



I'm not saying that you should not repair your microwave, but as a general rule, I would not recommend it:


  Careless troubleshooting of a microwave oven can result in death or
  worse. Experienced technicians have met their maker as a result of a
  momentary lapse of judgement while testing an oven with the cover
  removed. Microwave ovens are without a doubt, the most deadly type of
  consumer electronic equipment in wide spread use.
  
  The power supplies for even the smallest microwave ovens operate at
  extremely lethal voltage and current levels. Do not attempt to
  troubleshoot, repair, or modify such equipment without understanding
  and following ALL of the relevant safety guidelines for high voltage
  and/or line connected electrical and electronic systems.
  
  We will not be responsible for damage to equipment, your ego, county
  wide power outages, spontaneously generated mini (or larger) black
  holes, planetary disruptions, or personal injury or worse that may
  result from the use of this material. -- http://www.repairfaq.org/sam/micfaq.htm


"Try this instead"

For most people, replacing the unit or professional repair is a more reasonable risk.