Maintain And Repair Electronically-Controlled Domestic Appliances PDF

## Quarter III ### LESSON: MAINTAIN AND REPAIR ELECTRONICALLY-CONTROLLED DOMESTIC APPLIANCE **Time Allotment:** 40 Hours ### I. INTRODUCTION: * This lesson contains information and suggested learning activities in Maintaining and Repairing a Toaster Oven. * Additionally, pre-testing and disassembl...

## Quarter III ### LESSON: MAINTAIN AND REPAIR ELECTRONICALLY-CONTROLLED DOMESTIC APPLIANCE **Time Allotment:** 40 Hours ### I. INTRODUCTION: * This lesson contains information and suggested learning activities in Maintaining and Repairing a Toaster Oven. * Additionally, pre-testing and disassembling-assembling procedure, as well as the parts and functions of a toaster oven are included to comply with the standard operating procedure. * There are forms to accomplish for proper documentation. ### PRE/DIAGNOSTIC ASSESSMENT **Directions:** Read each statement carefully and write the letter and word/s of your answer on a separate sheet of paper. 1. It refers to a domestic appliance that is considered a small oven used primarily to make bread brown and crisp. * A. Blender * B. Microwave Oven * C. Toaster oven * D. Vacuum Cleaner 2. In servicing any domestic appliance, a serviceman must have these for the information needed regarding the standard operating procedure. * A. Parts list * B. Safety instructions * C. Service manual * D. Troubleshooting guide 3. In repairing any domestic appliance, this is needed in order to disassemble the unit. * A. Service manual * B. Set of tools * C. Troubleshooting guide * D. Volt-Ohm-Milliammeter 4. In a toaster oven, it is responsible in producing high temperature. * A. Door * B. Heating element * C. Housing * D. ON light indicator 5. It is a rotating parts of the toaster oven that is responsible in the circulation of air around the food. * A. Convection fan * B. Crumb tray * C. Heating element * D. Housing 6. It is a turning knob used to set the cooking purpose of a toaster oven. * A. Function control knob * B. Power switch * C. Temperature control knob * D. Timer knob 7. It is used for us to view the food inside the toaster oven. * A. Display * B. Function control knob * C. Glass door * D. Indicator 8. It is used to set the duration of cooking task of toaster oven. * A. Function control knob * B. Glass door * C. Temperature control knob * D. Timer knob 9. It is used to loosen and tighten screw of a toaster oven. * A. Blade cutter * B. Pliers * C. Screwdriver * D. Soldering iron 10. It is a measuring instrument used to check continuity and resistance of a circuit. * A. Ammeter * B. Ohmmeter * C. Voltmeter * D. Wattmeter ### LO1: PREPARE UNIT, TOOLS, EQUIPMENT AND WORKPLACE FOR MAINTENANCE/REPAIR * Prepare necessary tools, test instruments and personal protective equipment in line with job requirements * Acquire service manuals and service information required for repair/maintenance as manufacturer’s specifications * Conduct complete check-up of electronically-controlled domestic appliances * Document the identified defects based on check-up conducted #### INFORMATION SHEET 1.1 TOOLS AND MATERIALS IN MAINTAINING ELECTRONICALLY-CONTROLLED TOASTER OVEN In every electronic work, it is a must to prepare first the necessary tools, materials, and equipment needed as well as the information. The following list of tools, materials, and equipment are needed in maintaining and repairing a toaster oven: * Soldering Iron with stand * Soldering Lead * Desoldering Tool * Diagonal Cutting Pliers * Long Nose Pliers * Wire stripper * Adjustable Plier * PhilipScrewdriver * Flathead Screwdriver * Combination Wrench * Multitester/Volt-Ohm-Milliammeter (VOM) * Utility knife * Cable Tie * ESDWrist Strap * Mask * Non-Static Brush #### SELF-CHECK 1.1 TOOLS AND MATERIALS IN ΜΑΙΝΤΑΙNING ELECTRONICALLY-CONTROLLED DOMESTIC APPLIANCE (TOASTER OVEN) **Directions:** From the jumbled letters at the table below, find ten tools and instrument used in maintaining a toaster oven. Write your answer on a separate sheet of paper. ASRTGRDKAQTOPNMFGKLLSCVBNMRETUJD FCAZXCVNMFHLERHSAKLOSCFTDYUJHDBV GFLATSCREWDRIVERERRNNAREIVBNHJKY JDRTJCBNEWRTHJKLLOPGGBYYAYUIOPDC AXFGHNJKMTYUOLBFHKLNTLUJGRTHUJKI PHILIPSCREWDRIVERYΗΟΡΕΥΥΟΥGHWSRY KWODXTYURTHNMGFCVBESRTZCNVGHRTNB YCVNSOLDERINGIRONMGEΚΙΤΒAVCDEEYI SFMULTITESTERFHKLTEPDEVNLNMMNGFH THOSVBNMFHJKVBNMJKFLTRXZCFHJCRTH OESDWRISTSTRAPFGHJYIDGJHUNBMHCGJ OPLRYPGUSXCVBNMJGFDETYUITEDFHJKL AGHPHLSDDSFGHJKMNFFRERTYTYUIOPLD D UFGKGFGJURETHKLRAIOQWEIYKLMMDS POTHHLSTQFRTHJLLUEMASKRFNΑΕΥΙΟΖΝ LYQPYNGQVMOOTRVSGJRUEDVMGPLIERBB #### INFORMATION SHEET 1.2 OPERATION OF A TOASTER OVEN, PARTS and FUNCTIONS Toaster is an electrical or a typical small kitchen appliance used to toast a bread. Bread that is cut into slices and cooked at a high temperature to make it brown and crisp is referred as toast. Although, there are also toasters that are not electrically operated, instead, a fire or flame is used to toast bread products. This lesson will focus on electric toaster oven that is common nowadays in our kitchen. The toaster ovens at present are not just for toasting breads, instead the function was extended to other related tasks for particular purpose. The additional task are baking, roasting and broiling. There are lots of available toasters in the market to choose from. The three selections among toasters are pop-up toaster, toaster oven, and conveyor toaster. Toaster oven will be the focus of this lesson. Toaster oven is a small electric oven with front door, wire holder and a removable pan for roasting. This domestic appliance is considered as a miniature oven that allows you to bake and broil foods. Combination of heating elements is used to provide desired temperature for the purpose. As the unit is plugged-in to the power source, set of controls are turned to the desired level allowing the current to flow throughout the circuit. The heating element is energized and therefore produces equivalent temperature suited for the purpose. Timer switch sets how long the cooking takes and turns the unit off upon cycle completes. Several functions were incorporated to toaster oven nowadays resulting to additional control. Toaster oven may vary its capabilities and features depending on the brand, model, and application. The following procedures could be used as reference. **Toast function** This is used for toasting breads and other similar foods. All heating elements are used during this function. 1. Place the oven rack on the middle oven rails. 2. Turn the TEMP control knob to 450°F. 3. Turn the FUNCTION control knob to TOAST. 4. Place the food to be toasted on the oven rack. 5. Turn the TIME control knob to the required browning level. The POWER indicator turns on. (See owner's manual for preferred setting) 6. At the end of the toasting cycle, a bell will ring, to indicate the cycle has finished, and the appliance switches off. The POWER indicator turns off. **Bake function** This function provides constant and even heat suitable to be used for baking (cookies, cakes, and pies), and roasting (beef, pork, chicken, or other meat). All heating elements are used during this function. The convection fan circulates the hot air around the inside of the appliance. 1. Place the broil rack in the appliance. 2. Turn the TEMP control knob to the required temperature. 3. Turn the FUNCTION control knob to BAKE. 4. Preheat the appliance, if required, by turning the TIME control knob to the required time. The POWER indicator turns on. 5. Place the baking dish with the item/s to be baked on the broil rack. 6. Turn the TIME control knob to STAY ON or to the required time. The POWER indicator turns on. 7. If a time was set, a bell will ring at the end of the cycle, to indicate the cycle has finished, and the appliance switches off (POWER indicator turns off). 8. If no time was set, turn the TIME control knob to OFF when baking is completed. The POWER indicator turns off. **Roast function** The procedures given in the Bake function are the same. It is recommended to refer to the instruction manual of your appliance. **Rotisserie function** Do not to use a roast larger than 5lb. on the spit. Only the upper heating elements are used during this function. Chicken should be bound to prevent the legs or wings from separating during roasting and to allow the rotisserie assembly to rotate smoothly. It is recommended to use a meat thermometer to check the roasting progress. The procedures given in the Bake function are the same. It is recommended to refer to the instruction manual of your appliance. **Keep warm function** After 30 minutes, food may become dry and starts to spoil. 1. Place the broil rack on the oven rails in the middle of the appliance. 2. Turn the TEMP control knob to 180°F. 3. Turn the FUNCTION control knob to WARM. 4. Place the cooked food on the broil rack. 5. Turn the TIME control knob to STAY ON or as to required time. The POWER indicator turns on. 6. If the time was set, a bell will ring at the end of the cycle and the POWER indicator turns off. 7. Remove the food from the appliance, and then switch the appliance to off position by turning the TIME control knob to OFF. The POWER indicator turns off. **CAUTION:** Always wear oven mittens when placing or removing items from the appliance. Use caution when sliding the broil rack in and out of the appliance. ### A) Parts of a Toaster Oven (Manually Operated) Parts and components may vary due to brand, model and feature/s of toaster oven available. The following numbered parts are identified and its function defined on the next page. * 1 Door Handle * 2 Glass Door * 3 Lower Door Frame * 4 Temperature Control Knob * 5 Power Indicator * 6 Function Control Knob * 7 Timer Knob * 8 Power Cord * 9 Housing * 10 Griddle * 11 Griddle Cover * 12 Griddle Cover Handle * 13 Wire/ Broil/ Cooking Rack * 14 Bake/Roasting Pan * 15 Crumb Tray * 16 Rotisserie Removal Handle * 17 Tray Handle * 18 Rotisserie Skewer * 19 Drive mount * 20 Convection fan * 21 Two Rack Levels * 22 Upper heating elements (x2) * 23 Lower heating elements (x2) * 24 Pizza pan | **PARTS** | **FUNCTIONS** | |:---|:---| | Door Handle | A small round object or lever that is attached to the glass door and used for opening and closing it. | | Glass Door | Used to secure the food and temperature inside the toaster oven. A glass is used for viewing of food. | | Lower Door Frame | Part of the housing where the door hinges are fixed. | | Temperature Control Knob | A turning knob used to adjust the thermostat to the desired temperature. | | Power Indicator | To indicate that the toaster oven in ON. | | Function Control Knob | A turning knob used to set the cooking function to a desired setting. | | Timer Knob | A turning knob used to set the cooking time up to certain minutes and will turn the oven OFF at the end.| | Power Cord | Used to connect the appliance to the power source. | | Housing | A compartment where all parts of the toaster oven in place. | | Griddle | A piece of metal sheet or a pan placed on a cooker prior to cooking. | | Griddle Cover | Used to cover the food. | | Griddle Cover Handle | A small object or lever that is attached to the cover for holding purpose.| | Wire/ Broil/ Cooking Rack | This is used for toasting, baking, and general cooking with casseroles and other cookware. | | Bake/Roasting Pan | Used for all you're baking and roasting needs, attaches to Oven/Broil Rack. | | Crumb Tray | A removable part inside the bottom of the oven. | | Rotisserie Removal Handle | Used to safely remove/ replace the rotisserie. | | Tray Handle | Used to safely remove/ replace the tray. | | Rotisserie Skewer | Used in roasting purpose.| | Drive mount | The interface for the skewer. | | Convection fan | This is activated to provide air circulation around the food for faster and more even cooking. | | Two Rack Levels | To accommodate a variety of foods. | | Upper heating elements (x2) | Provide required temperature from the top. | | Lower heating elements (x2) | Provide required temperature from the bottom. | | Pizza pan | For broiling and baking pizza. | ### B) Parts of a Toaster Oven (Electronically-controlled) * 1 Control Panel * 2 LCD Screen * 3 PowerPlus™ Convection * 4 Function/Mode Control * 5 Start/Cancel * 6 Temp/Darkness * 7 Time/Slices/Size * 8 Temp/Timer * 9 Set * 10 Door Frame * 11 Flat Glass Door * 12 Door Handle * 13 Toast/Bagel * 14 Number of Slices * 15 Preheat Icon * 16 Pizza Size * 17 Temperature * 18 Convection * 19 Cook Time * 20 Pizza Pan * 21 Cooking Rack * 22 Bake Pan * 23 Crumb Tray #### SAFETY REMINDERS IN USING A TOASTER OVEN 1. Read carefully the instructions in the user’s/ operation/ owner’s manual before using a toaster oven. 2. Do not touch hot surfaces. Handles and knobs are provided for the user to easily open/close the glass door and to turn right or left the controls. Auxiliary parts are included in the package for holding purposes. 3. Keep away the cord, plugs, or appliance from the water or other liquid to avoid electric shock. 4. Unplug the toaster from outlet (power source) when not in use. 5. Do not use any appliance with a damaged cord or plug. 6. Before cleaning, unplug the cord and let the unit cool down prior to taking off parts for cleaning. 7. Place the appliance in stable position. 8. Do not use metal scouring pads in cleaning a toaster oven. This can damage the pad (buttons) and might cause electrical hazard. 9. Use only accessory that is recommended by the manufacturer to avoid injuries. 10. Keep at least four inches of space on all sides of the toaster oven to allow adequate air circulation during operation. 11. In case the plug is detachable from the unit, attach the plug to appliance first and then plug cord into the wall outlet. To unplug, turn the control to OFF first, and then remove the cord by grasping and pulling out the plug. Never pull the cord. 12. Do not use metal foil to cover Crumb Tray or any part of the toaster oven to avoid overheating. 13. When removing tray or disposing of hot grease or other hot liquids extreme caution must be observed. 14. Do not place unnecessary item on top of the oven during operation. The unit must be far from flammable materials (curtain, walls and the like). 15. Always wear protective, insulated oven mitts when putting in or removing items from the hot toaster oven. 16. Avoid scratching the glass door surface. 17. If the appliance malfunctions or has been damaged, seek technical assistance from servicemen for inspection, repair, or adjustment. #### SELF-CHECK1.2 OPERATION OF TOASTER OVEN, PARTS and FUNCTION **A. Directions:** Read each statement below and write the letter of your answer on a separate sheet of paper. 1. This is a small round object or lever that is attached to the glass door and used for opening and closing it. * A. Door Handle * B. Timer knob * C. Function control knob * D. Power switch 2. This is a turning knob used to set the cooking function to a desired setting. * A. Door Handle * B. Timer knob * C. Function control knob * D. Power switch 3. This is used to connect the appliance to the power source. * A. Power cord * B. Timer knob * C. Function control knob * D. Power switch 4. This is turned ON to provide air circulation around the food for faster and more even cooking. * A. Control switch * B. Convection fan * C. Function control knob * D. Power switch 5. This part illuminates when the timer knob of the toaster oven is turned ON. * A. Control switch * B. Power indicator * C. Function control knob * D. Power switch **B. Essay: Explain how the toaster oven operates (5 points).** * ***Sequence and transition of ideas were highly effective:*** * The toaster oven is a kitchen appliance that uses electric heating elements to heat and cook food. * The user can control the temperature and the time that the food cooks. * A thermostat regulates the temperature of the oven, and a timer controls the duration of the cooking cycle. * The toaster oven has different functions, such as toasting, baking, broiling, and roasting. * To use the toaster oven, the user must first select the desired function and temperature. * Then, the user can turn on the appliance and set the timer. * When the timer reaches zero, the appliance will shut off, and the food will be cooked. * The specific functions and settings of the toaster oven will vary depending on the model and brand. * The user should consult the owner's manual for specific instructions and safety precautions. #### INFORMATION SHEET 1.3 BASIC CONCEPT OF ELECTRONIC CONTROL (TRANSISTOR TIMER) Timer has a wide variety of uses specially when used with relay to include auto shut-off for safety of electrical appliances. For our lesson we will be concentrating in the timer using basic components like transistor, capacitor, resistor and LED. In the given diagram (Activity 1.4), the circuit is powered by a 3V battery. A switch is closed to start the timer causing the LED to switch OFF for a time period. After the time period is over, the LED will switch ON again. We have two transistors in the circuit and the operation (switching ON and OFF of LED) will happen alternately causing an alternating light effect. #### ACTIVITY 1.3 Electronic Timer Control **Directions:** Construct the given electronic circuit (Astable Multivibrator) using a breadboard. *[Image of circuit diagram]* #### ACTIVITY 1.4 RECEIVING A TOASTER OVEN (ELECTRONICALLY-CONTROLLED) FOR MAINTAIN/ REPAIR Directions: Provided with a defective Toaster Oven, use the Receiving and Repair Form to gather and document the information about the appliance at hand. Follow the procedures below: * **Resources:** Domestic appliance: Toaster Oven (electronically-controlled) Receiving and Repair Form * **Procedure:** 1. Conduct an initial interview to the owner of the appliance. * Ask what the problem is. * Request for the details of the problem (how does it happen/ since when/ nature of the problem) 2. As serviceman, you must recognize the problem/ complain. 3. Make an initial inspection of the appliance. * Physical appearance * Operating controls and other parts 4. Take note of the information gathered and observed. 5. Accomplish Maintain and Repair form. #### PERFORMANCE CHECK 1.4 RECEIVING ELECTRONICALLY-CONTROLLED DOMESTIC APPLIANCE FOR MAINTAIN/ REPAIR **Directions:** Read the questions and answer by checking the appropriate box. **Tasks:** 1. Recorded the name and address of the owner of the appliance? 2. Copied product/ brand/ name and serial number of the appliance? 3. Asked for complain and the remarks/ condition of the appliance? 4. Verified complain on the condition of the appliance? 5. Accomplished checklist of appliance parts condition. * Glass door * Knob of controls * Indicator lamp/s * Glass door handle * Rack/s * Display (if any) * Pan/s * AC cord #### LO2. DIAGNOSE FAULTS OF ELECTRONICALLY-CONTROLLED DOMESTIC APPLIANCES * Observe systematic pre-testing procedures in accordance with manufacturer’s instructions * Check and isolate circuits using specified testing procedures * Document results of diagnosis and testing accurately and completely within the specified timeframe * Explain identified defects and faults based on the result of diagnosis and testing * Provide data/information regarding the status and serviceability of the unit as per procedure #### INFORMATION SHEET 2.1 PRE-TESTING and TROUBLESHOOTING a TOASTER OVEN (ELECTRONICALLY-CONTROLLED) 1. Determine the specific problem by asking the symptom. * Ask the owner/operator of the toaster oven of what is the symptom of the unit. * Request some details of the symptom (how does the symptom happen and how long it has been observed). 2. Operate the device if possible. Make sure that you know how to operate a toaster oven. If not, review the operating manual as well as service manual (if available) of the unit prior to its testing and operation. * If you have worked on the same unit before, check out to see if it functions in the same way. * Determine the last time it has been modified/repaired. * You must recognize the symptom/complain of the owner to the unit. 3. Perform visual inspection of the unit. * Prepare the tools needed and remove the cover ready for inspection. * Apply careful physical inspection of the parts/components. (Look for burned and broken components; Inspect for loose connections or broken wires; Check for misaligned/ deformed parts) 4. If all looks fine, test the unit for resistance checks. * Get the multitester and set at lower range. Connect the test probes to each of the plug terminals, the reading must be infinite having the control/s at zero position. * Then, adjust slowly the timer, temperature, and functionknob, decrease in resistance should be observed upon turning the knob to the right. If this happens, the unit might be in good condition. For safety, place one probe across the plug terminals and the other probe to the body. There should be very high (infinite) resistance. If resistance is observed, do not attempt to plug the unit instead solve this first. Refer to troubleshooting guide in this lesson. 5. Record your findings for future reference. #### Diagnosing and Troubleshooting Procedure/ Guide: **SYMPTOM:** Toaster oven is not working. |**POSSIBLE DEFECT**| **PROCEDURE** | **CORRECTIVE MEASURE** | |:---|:---|:---| | Power cord | Check the continuity of the power cord using ohmmeter. | Replace power cord if necessary. | | Power source | Check the power at the outlet. | Insert the power plug into a different outlet. Reset the circuit breaker if necessary. | | Fuse | Check the continuity of the fuse using ohmmeter. | Replace fuse if necessary | **SYMPTOM:** Toaster oven is energized but not reach set temperature. | **POSSIBLE DEFECT** | **PROCEDURE** | **CORRECTIVE MEASURE**| |:---|:---|:---| |Door not closed | Check the door. Compare the thermostat setting and temperature. | Ensure the door is closed properly. Replace the thermostat if necessary. | **SYMPTOM:** Food not fully cooked. | **POSSIBLE DEFECT** | **PROCEDURE** | **CORRECTIVE MEASURE** | |:---|:---|:---| | Setting too low | Check the function setting as to requirements. Check the temperature setting as to requirements. Check the timer setting as to requirements. | Set the function setting as to requirements. Set the temperature setting as to requirements. Set the timer setting as to requirements. | **SYMPTOM:** Food over cooked or bunt |**POSSIBLE DEFECT**| **PROCEDURE** | **CORRECTIVE MEASURE** | |:---|:---|:---| |Setting too high | Check the function setting as to requirements. Check the temperature setting as to requirements. Check the timer setting as to requirements. | Set the function setting as to requirements. Set the temperature setting as to requirements. Set the timer setting as to requirements. | **SYMPTOM:** The skewer is not rotating. | **POSSIBLE DEFECT** | **PROCEDURE** | **CORRECTIVE MEASURE** | |:---|:---|:---| | Oversize food | Check the food on the skew for its size and part/s touching the housing.| Switch off the appliance and remove the skew to reduce size of food. Return the skew and continue the process. | **SYMPTOM:** The LCD display is not backlit. | **POSSIBLE DEFECT** | **PROCEDURE** | **CORRECTIVE MEASURE** | |:---|:---|:---| | Standby mode Backlight LED | Press any button to activate the screen and backlight. Check the temperature setting as to requirements. | Nothing to correct. If the screen display is ok, check the LED and replace if needed. | #### ACTIVITY SHEET 2.1 PRE-TESTING AND DIAGNOSING/ TROUBLESHOOTING AN ELECTRONICALLY-CONTROLLED TOASTER OVEN * **Resources:** Service manual of Toaster Oven Toaster oven (functional and defective) Activity sheet/ Forms Tools and Equipment Needed Pliers Screwdrivers Volt-Ohm Milliammeter Cleaning materials PPE * **Directions:** * Provided with the resources, perform the procedure and techniques in pre-testing and troubleshooting a toaster oven. * Let one of your classmate acts as the owner of the toaster oven subject for maintenance or repair. * Perform the procedures in accepting and pre-testing an appliance. * Accomplish Receiving and Repair Form and copy the form for diagnosis/troubleshooting in a separate sheet to be filled-up with necessary information as you perform the activity. * Provide information regarding the status and serviceability of the appliance. * Thirty minutes will be allotted for this activity. #### LO3 ΜΑΙΝΤΑΙN/REPAIR A TOASTER OVEN * Use PPE in accordance with OHS practices * Perform repair activity within the required timeframe * Observe safety precautions in handling the unit/product as per standard operating procedure * Replace defective parts/ components with identical parts or recommended parts with equivalent ratings * Solder/mount repaired or replaced parts/components in accordance with industry standards * Clean unit in accordance with standard operating procedure #### INFORMATION SHEET 3.1 PERSONAL PROTECTIVE EQUIPMENT (PPE) OCCUPATIONAL HEALTH AND SAFETY (OHS) POLICIES and PROCEDURE * **Personal Protective Equipment (PPE):** Personnel protective equipment is the employer's responsibility. It includes specially designed protective clothing intended for your protection. Wear the correct clothing and equipment to protect you from possible serious injury. Do not misuse any item provided for your health and safety. * **Personal Protective Equipment (PPE):** is defined in the Occupational Safety and Health Administration (OSHA) as a tool used to protect workers from injury or illness caused by having contact with the dangers (hazards) in the workplace, whether they are chemical, biological, radiation, physical, electrical, mechanical and other. Exposures to hazards are reduced using PPE. * **Occupational Health and Safety (OHS)** Occupational Health and Safety (OHS) is a cross-disciplinary area concerned with protecting the safety, health and welfare of people engaged in work. The goal is to promote a safe work environment. * **As Consumer Electronic Servicing National Certificate Level II (CES NC II) student:** you should know how to conduct yourself when working in the classroom/ laboratory room, as well as implement a safe way of accomplishing every task. Safety practices should be learned early and always adhered to when working with any electrical and electronic device. Each student has a responsibility to their colleagues and their organization to report and act upon any potential workplace hazard. All students need to be aware of the type of hazards that are possible in their work environment. #### SELF-CHECK 3.1 PPE/ OHS **I. Directions: Identify the body organ that must be protected from the listed source of danger. Write your answer on a separate sheet of paper.** 1. Too much sound with more than 85dB noise level. *Ears* 2. Fumes, dust and others that contribute to lack of oxygen. *Lungs* 3. Penetration of sharp objects, extreme temperatures, splashes of liquid chemicals or metals and the like. *Skin/ Body* 4. Catalyst powder, splashes of liquid chemicals or metal dust, radiation. *Eyes/ Skin/ Body* 5. Electric shock, exposure to chemicals, skin infections and extreme temperatures. *Skin/ Body* **II. Directions: Complete the statement below by supplying the missing word/s. Write your answer on a separate sheet of paper.** 1-3. Occupational Health and Safety (OHS)is a cross-disciplinary area concerned with protecting the *safety, health, and welfare* of people engaged in work. 4. The goal of OHS is to promote a *safe* working with any 5. Accessories/ jewelries are *not allowed* when working with any 6. Any potential workplace hazard must be *identified and controlled* electronic related devices or appliances. 7. All *workplaces* should be kept clear from all obstacles at all times. 8. All *hazards* must be *recorded and documented* in order to track the kinds of hazards in the workplace. #### INFORMATION SHEET 3.2 COMPONENT REPLACEMENT 1. Determine the description of the values and ratings of the individual defective parts using the manufacturer’s service manual. 2. Identify the sources of the replacement components/parts. Original replacement components from the original factory sources Universal replacement components from independent factory sources (Note: Always consider the physical size of the replacement part). 3. Consider the following factors in selecting parts. * Quality: the ability to provide exact specification of the replacement part * Tolerance: the ability to provide exact value or acceptable parameters of the replacement parts. * Availability: the local access to parts and availability * Price: refers to the affordability of the replacement parts 4. Disconnect or remove properly the electrical/mechanical parts of a toaster oven. 5. Install correctly the replacement parts/components 6. For burnt components where values are impossible to recognize, secure a schematic diagram or service manual if possible. In other case, you can look for the same brand and model as reference. 7. Double check the testing procedure in suspected defective components (on and off the circuit). 8. Check the nearby components for possible consequence of being damaged too. 9. Consider the original orientation/connection of the components in replacing defective one. 10. Observe safety at all times. #### SELF-CHECK 3.2 COMPONENT REPLACEMENT **Directions: Identify the term being described in each item.** 1. It is one of the factors to consider in selecting replacement parts that refers to the capability of local market to have the supply. *Availability* 2. It is one of the factors to consider in selecting replacement parts that refers to the conformity of the available parts as per acceptable specification. *Quality* 3. It is one of the factors to consider in selecting replacement parts that refers to the ability to provide exact value/ specification. *Tolerance* 4. It is one of the factors to consider in selecting replacement parts that refers to the affordability of the replacement parts. *Price* 5. It contains the necessary data of a particular domestic appliance including the schematic diagram. *Service Manual* #### INFORMATION SHEET 3.3 TROUBLESHOOTING TIPS 1. Conduct a quick diagnosis of the trouble symptom and repair the defective set in the shortest possible time. Do not troubleshoot atoaster oven unless you have determined the fault. Trace the fault from the mechanical section or electrical circuit section. 2. When troubleshooting integrated circuits (ICs) in the electrical/electronic circuit section, do not remove the IC from the PCB. Secure a circuit diagram from the manufacturer to help you identify and analyze the function of the IC. Consider the pin out of the IC. 3. When troubleshooting in the electrical/ electronic circuit section, prior to pre-testing, consider voltage measurement on components first before removing it for testing. If the measured voltage is normal, the component might be the cause of the problem. Either way, if the measured voltage is not normal (increased or decreased) the preceding circuit/components might be the cause. 4. If the trouble symptom is caused by aging components, the defective component is usually one of them. However, in high-power-handling circuits, a defective component may cause other components to malfunction. 5. Be familiar with the usual defects of components. (e.g. capacitors usually become leaky, shorted or open/resistor increase their resistance when they become defective/ semi-conductors such as transistors usually become open or shorted) 6. Don't replace an opened fuse or burned resistor unless you have corrected the trouble. 7. Check the mechanical switch circuit for its faulty contact before assuming defective electronic components. 8. When measuring resistance in the circuit, make sure that the circuit if OFF and power is not being supplied in the circuit, and that stored charges in capacitors are properly discharged. Failure to do so can damage the volt-ohm-milliameter (VOM) and the circuit due to the low resistance of the ohmmeter. 9. 9. While using a VOM for in-circuit resistance measurement, always exchange the setting of positive and negative probes. Take the higher meter reading with the approximate resistance. 10.Use soldering irons with the proper power rating to prevent the components and the circuit board from being overheated and damaged. Soldering iron tips should be cleaned and preferably slim. 11.Use proper tools and soldering aids when troubleshooting PCB. Ground the soldering iron to avoid damaging ICs and transistors. 12.Dry solder joints are hard to detect. However, when they are found or suspected, remove the components from the PCB; then, file or clean the leads and solder the joints back. Reheating dry joints with a new soldering lead is another remedy. When re-soldering, make sure you do not overheat the components. Overheating the PCB may cause the copper layer on it to warp and peel off. 13.Use Personal Protective Equipment. #### Maintenance of Toaster oven 1. Turn off the toaster oven and remove the cord from the source of voltage. 2. Apply lubricant to mechanical parts of the toaster oven that requires lubrication through a drop of oil or grease to assure smooth operation without grinding or squeaks. 3. Clean and check cooling louvers for any obstructions to avoid cutting off the air flow. 4. Clean or wipe dust and foreign particles at the PC Board and metal parts of the motor. 5. Replace worn or frayed AC cord and electrical wires. #### Cleaning Instructions After every use, it is important to clean all parts of the oven. This will prolong the life of your appliance. 1. Always switch off, unplug and allow getting cool before cleaning. Never use harsh abrasives or corrosive products. These could damage the oven surface. 2. Use damp cloth to wipe the exterior of the toaster oven. Dry immediately. Do not immerse in water. 3. Wipe the interior walls with a damp cloth and a mild liquid soap solution on a sponge. Dry immediately. 4. Slide out the crumb tray and discard to remove. Wipe clean and return. #### Procedure in Repairing a Toaster Oven * Once the specific electrical/mechanical problem is located: * consider the techniques for the proper removal of the defective component or parts; * anticipate what to do if the replacement part does not correct the problem; * and check the installation of the replacement or original part for any improper mounting in the mechanical assembly or circuit board. 2. Examine carefully the mounting of the replacement of original parts of the system. * Check the placement of the wires or leads of the replacement component. * Consider significant factors used in the original installation such as insulating toaster oven, silicon grease and locating mark for pin connections. * Observe proper placement of the component leads for electrical parts. 3. Perform the techniques for the proper soldering of electrical parts. * Be careful not to damage adjacent components. * Be careful not to lift the copper conductive path from circuit board base material. * Avoid any solder bridges between board paths. * Do not destroy the component being removed in case it is still functional and be careful not to damage the component being installed.