Need help?Do you have a question about the Panasonic NN-SD291S and is the answer not in the manual?
Explains how the High Voltage Inverter Power Supply controls output power via PWM signals.
Details the function of the Inverter Power Supply circuit, including voltage conversion for the magnetron.
Describes the Auto Control feature for inverter defrost and its operation sequence.
Explains Auto Sensor Cooking, using a humidity sensor to detect steam for automatic cooking.
Emphasizes the importance of proper grounding for microwave oven safety during repair.
Highlights high voltage and temperature hazards associated with the Inverter Power Supply.
Details troubleshooting steps when the 20A fuse blows, involving interlock switches and power relay.
Warns against inserting metal objects into the oven, which can cause microwave leakage.
Outlines checks required after repair, including screw tightness, connections, and leakage.
Advises caution due to sharp edges on internal parts during disassembly and reassembly.
Details continuity testing procedures for interlock switches and power relay RY1.
Explains how to test the continuity of the monitor switch with the door in different positions.
Describes continuity checks for the magnetron filament and case to diagnose faults.
Provides a test procedure to verify the function of the humidity sensor in the digital programmer circuit.
Details mounting and adjusting interlock and monitor switches to the door hook assembly.
Outlines a simple method for measuring microwave output power using water temperature rise.
Lists the necessary equipment for measuring microwave radiation leakage.
Details the step-by-step process for measuring microwave radiation leakage.
Explains leakage measurement after replacing the magnetron with the outer panel removed.
Describes leakage measurements on a fully assembled oven, checking door periphery and openings.
Specifies requirements for recording leakage readings and notifying authorities if limits are exceeded.
Provides failure codes (H95, H97, H98, H99) and troubleshooting steps for inverter and magnetron issues.
Lists main parts of the H.V. Inverter Board for identification and replacement.
Provides a visual exploded view of the oven assembly with numbered parts.
Lists replacement parts with reference numbers, part numbers, descriptions, and quantities.
Details the components and parts list for the oven's door assembly.
Lists the parts and components for the escutcheon base assembly, including the control panel.
Details the items included with the oven and the packing procedure for accessories.
Lists and describes the various lead wire harnesses used in the microwave oven.
Presents the detailed schematic diagram for the Digital Programmer Circuit.
Provides a parts list for components related to the Digital Programmer Circuit.
Explains how the High Voltage Inverter Power Supply controls output power via PWM signals.
Details the function of the Inverter Power Supply circuit, including voltage conversion for the magnetron.
Describes the Auto Control feature for inverter defrost and its operation sequence.
Explains Auto Sensor Cooking, using a humidity sensor to detect steam for automatic cooking.
Emphasizes the importance of proper grounding for microwave oven safety during repair.
Highlights high voltage and temperature hazards associated with the Inverter Power Supply.
Details troubleshooting steps when the 20A fuse blows, involving interlock switches and power relay.
Warns against inserting metal objects into the oven, which can cause microwave leakage.
Outlines checks required after repair, including screw tightness, connections, and leakage.
Advises caution due to sharp edges on internal parts during disassembly and reassembly.
Details continuity testing procedures for interlock switches and power relay RY1.
Explains how to test the continuity of the monitor switch with the door in different positions.
Describes continuity checks for the magnetron filament and case to diagnose faults.
Provides a test procedure to verify the function of the humidity sensor in the digital programmer circuit.
Details mounting and adjusting interlock and monitor switches to the door hook assembly.
Outlines a simple method for measuring microwave output power using water temperature rise.
Lists the necessary equipment for measuring microwave radiation leakage.
Details the step-by-step process for measuring microwave radiation leakage.
Explains leakage measurement after replacing the magnetron with the outer panel removed.
Describes leakage measurements on a fully assembled oven, checking door periphery and openings.
Specifies requirements for recording leakage readings and notifying authorities if limits are exceeded.
Provides failure codes (H95, H97, H98, H99) and troubleshooting steps for inverter and magnetron issues.
Lists main parts of the H.V. Inverter Board for identification and replacement.
Provides a visual exploded view of the oven assembly with numbered parts.
Lists replacement parts with reference numbers, part numbers, descriptions, and quantities.
Details the components and parts list for the oven's door assembly.
Lists the parts and components for the escutcheon base assembly, including the control panel.
Details the items included with the oven and the packing procedure for accessories.
Lists and describes the various lead wire harnesses used in the microwave oven.
Presents the detailed schematic diagram for the Digital Programmer Circuit.
Provides a parts list for components related to the Digital Programmer Circuit.
This document is a service manual for the Panasonic NN-SD291S and NN-SD291W Microwave Ovens, identified by order number PHAMOS1106067AE. It provides comprehensive information for servicing, troubleshooting, and maintaining these models.
The microwave ovens operate on a 120V AC single-phase, 60Hz power source, with a power requirement of 1440W and an output of 1100W. They utilize a microwave frequency of 2450MHz. The external dimensions are 29 7/8" (W) x 15 1/2" (D) x 16 7/16" (H) or 759mm (W) x 393mm (D) x 418mm (H). The oven cavity dimensions are 23 1/4" (W) x 14 7/16" (D) x 9 1/2" (H) or 591mm (W) x 367mm (D) x 242mm (H). The approximate weight is 55 lbs (25.0 Kg). These models are PbF (lead-free) compliant.
The microwave ovens feature variable power cooking control, managed by a Digital Programmer Circuit (DPC) that sends a Pulse Width Modulation (PWM) signal to the High Voltage Inverter Power Supply (U). This inverter circuit, unlike traditional microwave transformers, capacitors, and diodes, directly supplies 4,000V DC to the magnetron tube. The output power of the magnetron is continuously monitored by a current transformer within the inverter circuit, providing feedback to the DPC for precise power control.
The ovens offer various cooking settings:
A key feature is the "Inverter Turbo Defrost," which automatically determines cooking time based on selected weight (e.g., 1.0 LB defrosts in 5 min. 28 sec.).
The models incorporate "Auto Sensor Cooking" and "Sensor Reheat" functions. These features allow the oven to automatically determine the correct power level and cooking time without manual input. A humidity sensor element detects steam escaping from food, and the microprocessor calculates the remaining cooking time (T2 time) based on an initial T1 time and a K factor. The K factor varies with "More" or "Less" button selections. For example, in Oatmeal mode, if T1 is 2 minutes 40 seconds, T2 would be 16 seconds (160 sec * 0.1). Sensor Reheat is a quick and easy way to reheat refrigerated and room temperature foods, requiring only a button press.
The manual emphasizes safety precautions during servicing, particularly regarding the high voltage and high current circuits of the Inverter Power Supply (U). Servicing should only be performed by trained, qualified personnel.
The oven includes a self-diagnostics failure code system (H95, H97, H98, H99) to indicate magnetron and inverter circuit problems. The manual provides a flowchart for troubleshooting these codes, including checks for magnetron filament continuity, inverter input AC voltages, and inverter control signals.
The manual explicitly states: "DO NOT try to REPAIR H.V. Inverter power supply (U). Replace complete H.V. Inverter(U) Unit." This is due to the extreme danger associated with repairing these high voltage, high current circuits without proper test equipment. Defective inverter boards must be replaced with new ones.
Procedures are outlined for testing:
The manual also includes exploded views, parts lists (including lead-free solder PCBs indicated by "PbF" stamp), and schematic diagrams for the digital programmer circuit and wiring materials. It notes that PbF solder has a higher melting point (30-40°C higher than standard solder) and requires a high-temperature soldering iron (370 ± 10°C), with eye protection recommended due to splashing.
General| Brand | Panasonic |
|---|---|
| Model | NN-SD291S |
| Category | Microwave Oven |
| Language | English |
To Next Page