DAEWOO microwave oven fault, not heating, blown fuse + faulty magnetron, grounded.

ID: 239486

Description:

Steps:

  1. WARNING, always remember that microwaves are dangerous whether they are connected to the power grid or disconnected due to the voltage that can remain accumulated in the HV capacitor, up to 2000 V. Safety measures must always be followed.
  2. IF YOU ARE NOT QUALIFIED, LACK TECHNICAL KNOWLEDGE OF ELECTRICITY, AND DO NOT HAVE THE TECHNICAL MEANS, DO NOT ATTEMPT THIS REPAIR, AS IT CAN BE VERY DANGEROUS - FATAL IF YOU SUFFER AN ELECTRIC SHOCK.
  3. A check of the microwave, performed at a Repair Café. so I don't have as many photos as I would like. The unit would turn on, but it did not heat up. We checked for the classic fault of the high-voltage fuse located at the output of the transformer, and it was blown.
  4. Before installing a new fuse and testing to see if it would blow again, sacrificing a fuse, we checked several components to try to identify the reason for the fuse blowing.
    5. Step image Step image
  5. With the device disconnected from the mains and the 2 terminals of the lower capacitor bridged for safety, remove the fuse to check it; it is blown.
    6. Step image Step image
  6. 2nd Check: Since we have a capacitance meter, we check the capacity of the high-voltage capacitor, which is correct at approx. 1 uF.
  7. 3rd Check: We remove the high-voltage diode and check it with the test cable with a light bulb, since we do not have a 12 V or 48 V power supply to test it with the help of a 2.2 kOhm resistance.
  8. The various checks that can be performed on the CAPACITOR can be seen in several videos I have on YouTube LINK.
  9. The various checks that can be performed on the DIODE can be seen in several videos I have on YouTube from a few years ago. LINK.
    10. Step image Step image Step image
  10. Having ruled out the capacitor and diode, I verify that the 230 V mains supply is reaching the transformer input; here is a video where I explain this test, to be performed using some cables and a light bulb.
  11. LINK to the video.
  12. All that remains is the Magnetron measurement; of course, one could have proceeded to check this first, but it is usually more likely for the fuse, capacitor, or input power supply to fail than the transformer itself. Troubleshooting is most often a process of ruling out components: test it, it's okay, next...
  13. In this case, the MAGNETRON (the component that generates microwaves) is faulty, SHORTED TO GROUND, so the high voltage reaching the winding drops to 0, shunted to ground.
    14. Step image Step image Step image
  14. We compared the measurement with another magnetron from a similar model and that one shows correct insulation, so the fault lies with the magnetron. By personal decision of the user, who came to us at Repair Café Palma (Spain), the expense of purchasing a new magnetron is not worth it to them, and they decided not to repair the microwave,
  15. donating it to us to scrap and obtain spare parts.
  16. End of the Guide, other Microwave repair guides: Microwave Oven
    17. Step image Step image Step image
Back