1)High frequency can not be used. 

①The door switch behind the case is not closed. Open the door and push out the button of the door switch.We are provide HF vacuum wood drying machine and HF board jointing machine、HF Bentwood Press Machine、HF( RF) Generator,you can buy it.

②"High Pressure Open" button contact is not good, repair or replace the button.

③The tube filament is not bright, check whether filament voltage is normal. If the voltage is normal, remove the connecting screw of the filament thread, polish the connection point and connect again.

④Check if the internal connection is disconnected

2)There is fire phenomenon in high frequency.

①Look at the location of the fire and polish it with fine sandpaper.

②Anode or grid current is too large, adjust to the right position.

③Check if there is a short circuit in the load workpiece.