PANASONIC Inverter NN-SD28HS Microwave - Dead, faulty Schottky diode in the switched-mode power supply.

ID: 205460

Description:

Steps:

  1. A simple document of a repair we performed at Repair Café Palma in January 2026; I don't have many photos, and the ones I do have are not of great quality since I focused on the repair, as time is money at Repair Cafés and we don't have much of it.
  2. The oven was dead. It had 230 V input voltage, and there was power up to the input of the electronic board. Since it is a model with a display, keep in mind that the electronic board is always powered, but the display would not turn on or react.
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  3. The high-voltage inverter module (white module) is shown in the photo, indicated by the green arrow, disassembled; it is NOT necessary to disassemble it, the fault is not in this component.
  4. The reason the oven does not turn on and appears dead is a short-circuited Schottky diode in the center of the electronic board.
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  5. The first thing I checked was that we had 230 V voltage (the country's electrical grid) at the power input and that this voltage reached the electronic board input (central white connector at the top, Orange and Purple wires).
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  6. After checking several components on the board, I measured the Schottky diode in the center of the board under the small transformer, and it showed a short circuit between its two terminals.
  7. The second check performed was to cut one leg of the diode to be able to measure it while isolated. CAUTION: DO NOT CUT IT FLUSH; we cut it in such a way that if the diode measured OK while isolated, it could be reattached with a solder point.
  8. It showed the same measurement while isolated, so I removed the diode and soldered a similar Schottky type since I did not have the exact one.
  9. FAULTY SCHOTTKY MODEL: SB 2100HF
  10. SUBSTITUTE USED: SR2150 DO-15
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  11. Once the diode was replaced and the PCB and the console were reassembled, the oven was powered on and turned on right away. I am sorry I do not have more specific photos.
  12. As we can see, the oven is working. The fault was only caused by the SB 2100HF Schottky diode.
  13. End of Guide.
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