If it's a burning odor, and there's a buzz, or a hum that's louder than normal, failure of the the high voltage transformer or high voltage rectifier would be the most likely cause. A failed rectifier usually looks like it's been hot - may have small bubbles on the surface, or may be discolored. A transformer will emit smoke when 120 volts is applied to the primary. Keep in mind that these things run on 4000 volts, or more. You can easily be electrocuted poking around inside when the unit is running (the capacitor may stay charged with 4000 v for weeks or months even when the unit is off). if you don't have a working knowledge of electronics / electricity, it's best to find someone who does. If the rectifier is bad, make sure you discharge the capacitor with a screwdriver from terminal to terminal, and from each terminal to ground. It isn't pleasant having a 4000 volt jolt of electricity travel through your finger. I know from experience. You finger will light up nicely for a second, though. It's kind of neat, but painful!
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