Assessment-Reviewer.docx

Ranges to be used in testing voltage outputs of the different STAGES of the POWER SUPPLY TRANSFORMER STAGE: PRIMARY WINDINGS -- 250VAC SECONDARY WINDINGS -- 50VAC RECTIFIER STAGE: (Diode outputs) -- 50 VDC FILTER STAGE: (Capacitor terminals) -- 50VDC REGULATOR STAGE/FINAL OUTPUT: 50VDC Defects...

Ranges to be used in testing voltage outputs of the different STAGES of the POWER SUPPLY TRANSFORMER STAGE: PRIMARY WINDINGS -- 250VAC SECONDARY WINDINGS -- 50VAC RECTIFIER STAGE: (Diode outputs) -- 50 VDC FILTER STAGE: (Capacitor terminals) -- 50VDC REGULATOR STAGE/FINAL OUTPUT: 50VDC Defects that may occur on the following electronic components. 1. Diode-OPEN,SHORTED (Rx10) 2. Capacitor- OPEN,SHORTED,LEAKY (use high range for low value capacitors and vice versa) 3. Transistor- SHORTED, OPEN (Rx10) 4. Resistor- SHORTED, OPEN, CHANGE IN RESISTANCE (range to be used is based on the third stripe) Parts and functions 1. LCD TV - LCD front panel - Responsible for producing the visual output - Backlight - Responsible for illuminating the display - Power Board -- Convert AC to DC and responsible for distributing power - Mainboard -- Coordinates the function of various components - Jackpack section -- Contains ports for external devices - Inverter Board -- Converts DC to AC for backlight power 2. WASHING MAHINE - Motor -- Responsible for the rotation of drum/pulsator. - PCB -- control panel location - Timer -- set the wash time for your cycle - Fuse -- protects the unit from electric overload - AC chord -- Connects the unit to the power source 3. MICROWAVE OVEN - Magnetron -- Produces microwave for heating food - Oven Lamp -- Provides illumination on the chamber - High voltage transformer -- Steps up the primary voltage to a high voltage - Waveguide -- Directs the flow of microwave to the cooking chamber - Turntable -- Gives proper distribution of heat by turning - High voltage capacitor - works along with the high-voltage diode to effectively double the already-high voltage from the secondary (output) winding of the power transformer. - Rectifier diode - works along with the high-voltage capacitor to effectively double the already-high voltage that is provided by the power transformer. - Thermal cut-out/Thermostat -- Protects the unit from overheating LCD Television +-----------------------+-----------------------+-----------------------+ | Component/Part | Faults/Defects | Remedies/Checks to be | | | | made | +=======================+=======================+=======================+ | 1. Timing control | 1-3. White Display, | Replace board/ | | board | No display, Double | speaker/ LCD | | | image, Display | | | 2. Inverter Board | distortion (black and | | | | white vertical bars | | | 3. Main board | on the screen). | | | | Multiple | | | 4. Power Board | vertical/horizontal | | | | lines across the | | | 5. Jack pack section | screen.  | | | | | | | 6. Speakers | 4. No power, low | | | | power, power | | | 7. Liquid Crystal | blink and | | | Display | intermittent no | | | | power. | | | | | | | | 5. No sound, | | | | distorted | | | | sound, High | | | | Pitched whine, no | | | | TV reception, | | | | unable to tune to | | | | certain blocks of | | | | channels, | | | | channels change | | | | randomly. | | | | | | | | 6. No audio output | | | | | | | | 7. White Display, No | | | | display, Double | | | | image, Display | | | | distortion (black | | | | and white | | | | vertical bars on | | | | the screen). | | | | Multiple | | | | vertical/horizont | | | | al | | | | lines across the | | | | screen | | +-----------------------+-----------------------+-----------------------+ Washing machine +-----------------------+-----------------------+-----------------------+ | Faults/Defects | Suspected Part | Remedies/Checks to be | | | | made | +=======================+=======================+=======================+ | 1. No power | 1. AC chord, fuse, | 1. Check to ff. | | | dirty contacts, | components using | | 2. Weak pulsator | open motor | ohmmeter (Rx10) | | rotation | windings, | | | | defective | Replace any | | 3. No rotation but | capacitor and | shorted or open | | there is sound | defective timer | component. | | coming from the | | | | motor | 2. Belt, gearbox, | 2. Check the tension | | | | of the belt and | | 4. Water doesn't | 3. Belt, gearbox | check if there | | drain | | are any play on | | | 4. Drain knob, | the gearbox. | | 5. Pulsator rotates | rubber plug | | | in only one | | 3. Check the tension | | direction | 5. Wash selector, | of the belt and | | | timer, foreign | check if there | | | materials jammed | are any play on | | | the pulsator | the gearbox. | | | | | | | | 4. Check the | | | | connection | | | | between the drain | | | | knob and rubber | | | | plug. | | | | | | | | 5. Check for any | | | | foreign materials | | | | that can cause | | | | the pulsator to | | | | sieze. | +-----------------------+-----------------------+-----------------------+ Give the causes and checks to be made on the following troubles of a microwave oven. +-----------------------+-----------------------+-----------------------+ | Faults/ Defects | Cause | Inspection/Remedies | +=======================+=======================+=======================+ | 1. No power | 1. AC chord, fuse, | 1. Check to ff. | | | diode, capacitor, | components using | | 2. Doesn't light | transformer | ohmmeter (Rx10) | | | | | | 3. With power but no | 2. Oven lamp | Replace any | | display | | shorted or open | | | 3. Circuit board | component. | | 4. With power but | | | | unit doesn't heat | 4. Magnetron | 2. Replace oven lamp | | | | | | | | 3. Isolate and test | | | | any suspected | | | | component from | | | | the PCB. If the | | | | components are | | | | impossible to | | | | check, replace | | | | the PCB with an | | | | identical one. | | | | | | | | 4. Test the | | | | magnetron | | | | terminals | | | | (fig. 1) | +-----------------------+-----------------------+-----------------------+