Sharp R-22JT Service Guide

Sharp R-22JT Manual

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  • Sharp R-22JT | Service Guide - Page 1
    Sharp Electronics Corporation Servicing Commercial Microwave Ovens R21JC/21HT & R22GTF/R22JT
  • Sharp R-22JT | Service Guide - Page 2
    Len Hahn Senior Manager, Field Services & Support These ovens should not be adjusted or repaired by anyone except properly qualified service personnel.
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    Objective This course has been designed around the R22JT Commercial Microwave Oven. All disassembly and testing procedures refer to the R22JT only. While most heavy duty ovens are quite similar please refer to the specific model you are working on. Your have information on all four
  • Sharp R-22JT | Service Guide - Page 4
    Technologies Quiz 1. What is Microwave energy? a. Energy created by nuclear radiation. b. Energy created by chemical reaction. c. Energy created by electromagnetic generation d. Energy created by atomic fusion 2. What is the frequency
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    b. from the inside to the outside. c. only from the top. d. only from the bottom. 4. Why does food sometimes appear to cool faster when cooked in a microwave than when cooked in a conventional oven? a. Microwave energy does not last as long in certain foods and allows heat to escape. b. Because
  • Sharp R-22JT | Service Guide - Page 6
    the food to cool before eating. c. Allows the cooking container to cool before handling. d. Allows the food to finish cooking. 6. When can metal be used inside a microwave oven? a. When you want the food not to over cook. b. When you want to generate more heat. c. When you want to protect your oven
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    resistance within the electrical circuits even when power is removed. d. The high wattage output from the magnetron. 8. When working on a microwave after disconnecting the power cord from the outlet and removing the cabinet, the technician must: a. discharge the high voltage capacitor b. check
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    Technologies Quiz 9. How often must a microwave oven be tested for leakage? a. Anytime after service. b. Only if the customer complains of headaches. c. Only if the door or door switches are repaired. d. Only if the magnetron is replaced. 10. To comply
  • Sharp R-22JT | Service Guide - Page 9
    R-21JCA Control Panel 1000 Watts
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    R-21JCA Oven diagram Air ventilation cover and openings Ceramic shelf Rotary antenna Air intake openings
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    R-21JCA Ceramic Shelf Removal Using a putty knife, lift up from underneath the ceramic shelf to remove shelf from cavity. Be careful not to damage the rubber fins. Rubber fins No rubber fin
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    R-21JCA Ceramic Shelf Installation Rubber fins No rubber fin Position the front of the shelf with the front of the oven. The front edge of the shelf does not have a rubber fin. Push down on the rear of the shelf to complete the installation taking care not to damage the rubber fins.
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    R-21JCA Schematic
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    to step-up or step-down an applied AC voltage •The High Voltage transformers that are used in microwave ovens are the step up type Input= 120 volts Secondary Output= 2400 volts •The 22JT employs two 1:20 step up transformer which outputs 20 volts for every volt applied to the primary •When we
  • Sharp R-22JT | Service Guide - Page 15
    Transformers Primary •Secondary current is inversely proportional to the turns ratio •Available output current in our 1:20 step up transformer will be 20x less than the current on the primary Input= 8 amps Secondary Output= 400 ma •The high voltage doubler circuit will double the transformer
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    Danger
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    Electrocution
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    R-21JCA Single Magnetron
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    High Voltage Doubler Operation
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    High Voltage Doubler Operation Doubler charging Doubler Discharging "Voltage Adding"
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    Magnetron Operation ¼ wave antenna Anode Resonant Cavity Cathode & Heater Magnet around resonant cavity not shown
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    Interior of Magnetron
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    R21JCA Trouble shooting tips 1. Magnetron temp fuse open = Check magnetron venting and timer operation. This unit is susceptible to get set to run without food load. 2. Oven
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    R-21JCA Schematic
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    R-22JT Schematic 1200 Watts
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    R22/25JT Disassembly Procedures Units can be stacked for some restaurant applications. In this case, the units need to be separated by removing the fixing angle before servicing.
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    CRITICAL SAFTEY WARNING WARNING! You can be seriously INJURED or KILLED from the High Voltage circuit inside the Microwave Oven Disconnect AC Power and discharge the HV circuit before servicing
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    Outer Case Cabinet Removal Disconnect AC power before Cabinet removal; this will give the HV Doubler Circuit time to Discharge
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    Outer Case Cabinet Removal Remove 2 screws on each side Remove 7 screws, which are placed around the perimeter of the cabinet
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    Outer Case Cabinet Removal Tilt the cabinet upwards to release, and lift away You now have access to the HV circuit and control unit
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    WARNING, HIGH VOLTAGE Using a screwdriver with an insulated handle; short together the two terminals of each High Voltage Capacitor H.V. Capacitors Short terminals with screwdriver
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    Rear Cabinet Removal Remove 8 screws Machine thread Note: These 2 screws are brass Lift up the rear cabinet; be careful not to break the AC Line connectors
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    Rear Cabinet Removal You can gently lay down the rear cabinet on top of the unit or You can disconnect the 2 AC Line connectors and remove the 1 grounding screw to completely remove the rear cabinet
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    Rear View Upper Magnetron (1) White connector Lower Magnetron (2) Blue connector Rear View
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    Right Side View H.V. Capacitor for Upper Magnetron High Voltage Rectifier Ass'y for Upper Magnetron Noise Filter Blower Motor Power Transformer for Upper Magnetron (Note: White Connectors on Harness)
  • Sharp R-22JT | Service Guide - Page 36
    No Case positive lock connectors
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    Right Side View H.V. Capacitor for Lower Magnetron Latch Hook Ass'y Control Unit High Voltage Rectifier Ass'y for Lower Magnetron Power Transformer for Lower Magnetron (Note: Blue Connectors on Harness)
  • Sharp R-22JT | Service Guide - Page 38
    Control Panel Removal Remove the air intake filter Ass'y Gently pull the locks straight out to remove filter
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    Control Panel Removal Remove 2 screws Slide control panel down to release
  • Sharp R-22JT | Service Guide - Page 40
    Control Panel Removal Mark down the position of all connectors on a piece of paper, and remove all 9 connectors. Be sure to connect the cables in their exact original positions on the new control board
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    Control Panel Disassembly Key Unit Control Unit Remove 5 screws Front View Rear View
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    Control Panel Disassembly Lift up on the lock of cable connector; CN-G to release the lock Gently pull up on the Key unit cable
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    Control Panel Disassembly Control Panel Frame with Key Unit Control Unit
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    Door Removal Remove 4 screws, 2 screws per hinge These screws can be very tight; you may need a pliers or wrench to loosen before using a screwdriver
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    Door Removal Open door and carefully pull door straight out Door removed from unit
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    Door Installation Install door and tighten screws on the upper and lower hinges Apply Gorilla glue and test for normal latch hook operation and leakage before glue dries, adjust door if necessary
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    Door Disassembly
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    Lower Stirrer Motor Access •Snip off •Bend sharp edges with pliers •Replace cover with screw
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    R25JT Schematic 2100 Watts Voltage Switches
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    R25JT Voltage Switches EE4 EE5 The R25JT utilizes Voltage Switches to select the input voltage between 208 and 230 volts, since power sources vary. Note: The oven will display an EE4 or EE5 if the voltage switch is set incorrectly. Always measure the line voltage before adjusting the voltage switch.
  • Sharp R-22JT | Service Guide - Page 51
    How to set Voltage Switches
  • Sharp R-22JT | Service Guide - Page 52
    Monitor switch 2 Monitor switch 1 Latch Hook Ass'y • Monitor Switches; each high voltage circuit has its own monitor switch, which is used to detect a door latching failure. The monitor switches will shunt across the AC line and open the main fuse if activated, disabling the unit. The
  • Sharp R-22JT | Service Guide - Page 53
    Hook Ass'y Secondary interlock switch 2 Secondary interlock switch 1 • Secondary interlock Switches; each high voltage circuit has its own secondary interlock switch, which is used to supply AC line voltage to each high voltage circuit. The secondary interlock switches close when the door is shut.
  • Sharp R-22JT | Service Guide - Page 54
    Latch Hook Ass'y Door sensing switch • The door sensing Switch; senses if the door is open or closed. In addition, it is also used in the standby mode. • Standby mode; operates the blower motor to cool the magnetrons when the door is opened. The oven light operates too. The
  • Sharp R-22JT | Service Guide - Page 55
    Control Panel Schematic Foil pattern Primary interlock relay 1 Primary interlock relay 2 Door switch Oven Magnetron thermistor thermistor Key unit
  • Sharp R-22JT | Service Guide - Page 56
    Control Panel • Primary interlock relays, 1 & 2; apply AC line voltage to each power transformer which supplies the doubler circuits with 2400 volts for magnetron operation.
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    Control Panel Exhaust duct Oven thermistor; is located on the exhaust duct and is used to measure the exhaust air temperature. Oven thermistor
  • Sharp R-22JT | Service Guide - Page 58
    Control Panel Magnetron thermistor Magnetron thermistor; is used to measure the air temperature around the upper magnetron, which can cause the unit to shut down. This also protects the lower magnetron from overheating
  • Sharp R-22JT | Service Guide - Page 59
    Control Panel The key unit is a matrix of switches that is used for selecting the cooking process
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    Control Panel Foil patterns The very fine foil patterns acts as a fuse and will open under excessive current draw
  • Sharp R-22JT | Service Guide - Page 61
    Troubleshooting THE UNIT MUST REMAIN DISCONNECTED FROM AC POWER AT ALL TIMES UNLESS SPECIFIED Disconnect the primary coils of each power transformer and leave disconnected until all troubleshooting activities have been completed
  • Sharp R-22JT | Service Guide - Page 62
    Troubleshooting the Noise Filter • The noise filter is employed to meet FCC regulations by not allowing the 2450Mhz RF energy to travel out of the unit via the AC power lines. • A faulty noise filter will cause a no power condition. • The 20 Amp fuse is also located on the noise filter.
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    Troubleshooting the Noise Filter N Disconnect wires from noise filter before proceeding L
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    Troubleshooting the Noise Filter N W
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    Troubleshooting the Noise Filter L R
  • Sharp R-22JT | Service Guide - Page 66
    Troubleshooting Control Panel "Dead" Key unit CN-B CN-4 Disconnect all wire harnesses except the AC input connector CN-4 and the door sensing switch connector CN-B. (the door sensing switch will not effect a dead unit) Disconnect the Key unit connector CN-G
  • Sharp R-22JT | Service Guide - Page 67
    Troubleshooting Control Panel "Dead" Pin 1 Pin 7 Measure 120 volts at pins 1 & 7 of CN4 If 120 volts is present, proceed with foil pattern check If 120 volts is not available, check the noise filter / fuse, and check the oven temperature fuse if required
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    Troubleshooting Control Panel "Open Foil Pattern" Visually inspect varistor and check for burns
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    Troubleshooting Control Panel "Open Foil Pattern" Using a VOM, measure the coil resistance of the primary winding of the transformer Check for 270Ω±10%
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    Troubleshooting Control Panel "Open Foil Pattern" Check for open foil patterns points "a" and "b" on the PWB c a b J1 d Foil Repair Procedure
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    Troubleshooting Key Unit Key unit CNB CN4 Disconnect all wire harnesses except the AC input connector CN-4 and the door sensing switch connector CN-B. Disconnect the Key unit connector CN-G
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    Troubleshooting Key Unit Connect AC power cord to wall outlet and open the oven door The blower and oven light will turn on indicating that the control panel is OK, however, the key unit must be shorted
  • Sharp R-22JT | Service Guide - Page 73
    Troubleshooting Key Unit Momentarily shunt across pins 1 7&10 of the key unit connector CN-G If a beep is heard the key unit is 7 defective 10 If the control panel does not beep, the control panel is defective DISCONNECT AC POWER CORD FROM WALL OUTLET!
  • Sharp R-22JT | Service Guide - Page 74
    Troubleshooting Door Switch Door switch Note: orange wire Confirm the latch hook is activating the plunger of the door switch when the door is open Using a VOM, measure across the door switch contacts and check for continuity when the door is closed Open the door and now check for an open circuit
  • Sharp R-22JT | Service Guide - Page 75
    Troubleshooting the Primary Interlock Relays CN-G CN-B CN-4 Disconnect all wire harnesses except the AC input connector CN-4, door sensing switch connector CN-B and Key unit CN-G
  • Sharp R-22JT | Service Guide - Page 76
    Troubleshooting the Primary Interlock Relays Relay 1 Relay 2 Connect AC power cord to wall outlet Start cook process and measure for continuity across primary interlock relays 1 and 2 Note: "EE3" will appear on display after 9 seconds DISCONNECT AC POWER CORD FROM WALL OUTLET!
  • Sharp R-22JT | Service Guide - Page 77
    R-21JCA Control Panel J-1 RY-2 Power transformer RY-1 Oven lamp, stir motor, fan motor
  • Sharp R-22JT | Service Guide - Page 78
    R-21JCA "Open Foil Pattern" J1 c ba d Check for open patterns points "a" and "b" on the PWB Foil Repair Procedure
  • Sharp R-22JT | Service Guide - Page 79
    Troubleshooting Using Fault Codes Please refer to the following fault code tables in the respective Service Manuals to further troubleshoot each model: R22JT Page 11 R25JT Page 12 R21JCA Does not use fault codes
  • Sharp R-22JT | Service Guide - Page 80
    R22JTF Error code reference
  • Sharp R-22JT | Service Guide - Page 81
    R22JTF Error code
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    R25JTF Error codes
  • Sharp R-22JT | Service Guide - Page 83
    Magnetron Thermistor "EE16" "EE17" There is only 1 magnetron thermistor, which is located on the upper magnetron If "EE16" is displayed on the control panel, the magnetron thermistor is "open" If "EE17" is displayed, the magnetron temperature is too high
  • Sharp R-22JT | Service Guide - Page 84
    Magnetron Thermistor "EE16" "EE17" To check the magnetron thermistor, disconnect the thermistor and measure with a VOM See chart below for normal resistance meter readings Magnetron thermistor connector
  • Sharp R-22JT | Service Guide - Page 85
    Oven Thermistor "EE6, "EE7" Exhaust duct Oven thermistor If "EE6" is displayed on the control panel, the oven thermistor has failed If "EE7" is displayed, the exhaust air temperature is too high. In this case you would need to check the filter, and be sure that the units air rear vents are not
  • Sharp R-22JT | Service Guide - Page 86
    Oven Thermistor "EE6, "EE7" Exhaust duct To check the oven thermistor, disconnect the thermistor and measure with a VOM See chart below for normal resistance meter readings Oven thermistor
  • Sharp R-22JT | Service Guide - Page 87
    Dual Magnetron Operation 120V Hot output of noise filter, via primary interlock relays 1 & 2 Common output of noise filter Power transformers are wired 180º out of phase
  • Sharp R-22JT | Service Guide - Page 88
    High Voltage Doubler Operation While the upper high voltage circuit is supplying power the magnetron, the lower high voltage circuit is charging.
  • Sharp R-22JT | Service Guide - Page 89
    Troubleshooting the Magnetron "EE1" EE2" "EE3" A failure of any high voltage component including the primary interlock relays on has started: EE1: magnetron 1 failure EE2: magnetron 2 failure EE3: magnetron 1 and 2 failure Refer to page 11 in R22JT service manual for complete troubleshooting chart
  • Sharp R-22JT | Service Guide - Page 90
    Troubleshooting EE1 and EE2 Troubleshooting techniques for fault codes EE1 and EE2 are common for each.
  • Sharp R-22JT | Service Guide - Page 91
    EE1 and EE2 1. To troubleshoot EE1 or EE2, make sure that you are checking the correct section relating to magnetron circuits and control section. Note: EE1, EE2, or EE3 usually
  • Sharp R-22JT | Service Guide - Page 92
    Troubleshooting EE1 and EE2 2. Remove primary wires from H.V. transformer and measure for 120v AC. If 120 volts or AC line input voltage is measured at the primary, would indicate that the problem would be strictly a H.V. or magnetron issue. The control circuits would be operating normally with AC
  • Sharp R-22JT | Service Guide - Page 93
    Troubleshooting EE1 and EE2 3. If 120 volts or AC line input voltage is not measured at the primary, the problem would be the control circuits; which includes the control panel, secondary interlock switches and latch hook ass'y.
  • Sharp R-22JT | Service Guide - Page 94
    Troubleshooting EE1 and EE2 Defective latch hook ass'y Only 1 secondary switch is activated, which is causing the EE1 fault code to display. 4. Check the latch hook
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    Troubleshooting EE1 and EE2 5. If the latch hook appears to be functioning normally, check for continuity across the switches. = zero ohms across each switch 6. Measure for
  • Sharp R-22JT | Service Guide - Page 96
    Troubleshooting EE1 and EE2 Relay 1 Relay 2 7. Check the primary interlock relays. Connect AC power cord to wall outlet Start cook process and measure for continuity across
  • Sharp R-22JT | Service Guide - Page 97
    parts. 8. If you found voltage at the primary of the H.V. transformer, then the problem is most likely to be a defective H.V. circuit or defective magnetron. Please follow the next few slides on how to troubleshoot the H.V. section and magnetron. Fault code EE3 would indicate the 2 H.V. circuits and
  • Sharp R-22JT | Service Guide - Page 98
    Troubleshooting the Power Transformers Disconnect primary winding and measure less then 1 Ω with an ohm meter
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    Troubleshooting the Power Transformers Disconnect secondary winding and measure approximately 106Ω
  • Sharp R-22JT | Service Guide - Page 100
    Troubleshooting the Power Transformers Disconnect filament winding between H.V capacitor and magnetron measure less than 1Ω
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    Troubleshooting the H.V. Doubler Diode Remove grounding screw and check rectifier With meter set at X1000 you should get a high resistance in one direction (forward bias)
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    Troubleshooting the H.V. Doubler Diode Reverse the leads of the ohm meter and you should read infinity (reverse bias) Note: Loose H.V. lugs wires can cause intermittent or no high voltage
  • Sharp R-22JT | Service Guide - Page 103
  • Sharp R-22JT | Service Guide - Page 104
  • Sharp R-22JT | Service Guide - Page 105
    Troubleshooting the H.V. Doubler Capacitor Remove one lead from the Capacitor and put the meter leads onto the capacitor terminals. You will see a momentary resistance reading and the meter will go back to infinity. Reverse the leads and you will see the same.
  • Sharp R-22JT | Service Guide - Page 106
    Troubleshooting the Magnetron Remove the leads from the magnetron and read the filament resistance. It should be less than one Ohm.
  • Sharp R-22JT | Service Guide - Page 107
    Troubleshooting the Magnetron Check to ensure you do not have a cathode to anode short. You should read infinity between the terminals and the case of the magnetron.
  • Sharp R-22JT | Service Guide - Page 108
    Microwave Output Power Test
  • Sharp R-22JT | Service Guide - Page 109
    Sharp Electronics Corporation This concludes our commercial microwave training
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Sharp Electronics Corporation
Servicing
Commercial
Microwave Ovens
R21JC/21HT &
R22GTF/R22JT