Phenomenon indicates normal 220V low voltage circuits. After repeated examine the various switches, high voltage diodes positive and negative resistance, cold resistance magnetron filament (1Ω), high-voltage capacitors and other parts were normal. Check voltage can be heated in the high voltage winding of the transformer (AC2100V), high voltage diodes two-terminal voltage (-4000V DC high voltage) were normal. So, I'm sure there is no problem components, there may be poor contact, but many times with alcohol swab to clean the connector, but failed to complete troubleshooting. Check again noted that all connectors and wires are squeezed together using clip card process connections, without the solder. Over time, the connections oxidation and oil, under the current state, because of too much pressure drop caused by the contact does not work. So with a fine sandpaper, a knife oxide wire and plug the root surface clean, then make rosin flux, solder all over again with the plug-ins is no malfunction. Note:-4000V DC voltage measurement, available with three tables in the 500 block 2500V DC external series resistor 5 10MΩ/1W to range extension to 5000V, can be measured.a4Uservice manual download site