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Troubleshooting Guide

Drawer Microwave

(Models MWD24-2 / MWD30-2)

5-3

#813632 - Revision B - December, 2009

MICROWAVE MEASUREMENT PROCEDURE

Requirements:

1.

Microwave leakage limit (Power density limit):  The power density of microwave radiation emitted by a microwave
oven should not exceed 1mW/cm2 at any point 5cm or more from the external surface of the oven, measured
prior to acquisition by a purchaser, and thereafter (through the useful life of the oven), 5 mW/cm2 at any point
5cm or more from the external surface of the oven.

2.

Safety interlock switches:  Primary interlock relay switch shall prevent microwave radiation emission in excess of
the requirement as above mentioned.  Secondary interlock relay and door sensing switch shall prevent
microwave radiation emission in excess of 5 mW/cm2 at any point 5cm or more from the external surface of the
oven.

Preparation for testing:

Before beginning the actual measurement of leakage, proceed as follows:

1.

Make sure that the actual instrument is operating normally as specified in its instruction booklet.

NOTES:

Survey instruments that comply with the requirement for instrumentation as prescribed by the performance stan-
dard for microwave ovens, 21 CFR 1030.10(c)(3)(i), must be used for testing.

Survey instruments that comply with the requirement for instrumentation as prescribed by CSA and NHW per-
formance standard for microwave ovens must be used for testing recommended instruments are, NARDA 8100
and NARDA 8200.

2.

Place the load of 275±15 ml (9.8 oz) of tap water initially at 20±5° C (68°F) in the center of the oven cavity.

The water container shall be a low form of 600 ml (20 oz) beaker with an inside diameter of approx. 8.5 cm (3-
1/2 in.) and made of an electrically non conductive material such as glass or plastic.

The placing of this standard load in the oven is important not only to protect the oven, but also to insure that any
leakage is measured accurately.

3.

Set the cooking control on Full Power Cooking Mode.

4.

Close the drawer and select a cook cycle of several minutes.  If the water begins to boil before the survey is
completed, replace it with 275 ml of cool water.

Leakage test:

Closed-drawer leakage test (microwave measurement):

1.

Grasp the probe of the survey instrument and hold it perpendicular to the gap between the drawer and the body
of the oven.

2.

Move the probe slowly, not faster than 1 in./sec. (2.5 cm/sec.) along the gap, watching for the maximum indica-
tion on the meter.

3.

Check for leakage at the drawer screen, sheet metal seams and other accessible positions where the continuity
of the metal has been breached (eg., around the switches, indicator, and vents).

While testing for leakage around the drawer, pull the drawer away from the front of the oven as far as is permit-
ted by the closed latch assembly.

4.

Measure carefully at the point of highest leakage and make sure that the highest leakage is no greater than
4mW/cm2, and that the primary interlock switch/secondary interlock relay does turn the oven OFF before any
door movement.

Содержание MWD24-2

Страница 1: ...he outer cabinet case removed See CAUTION above In this event 1 Disconnect the power supply cord and then remove outer cabinet case 2 Open the door and block it open 3 Discharge high voltage capacitor See WARNING above 4 Disconnect the leads to the primary of the power transformer 5 Ensure that the leads remain isolated from other components and oven chassis by using insulation tape 6 Only after p...

Страница 2: ...testing recommended instruments are NARDA 8100 and NARDA 8200 2 Place the load of 275 15 ml 9 8 oz of tap water initially at 20 5 C 68 F in the center of the oven cavity The water container shall be a low form of 600 ml 20 oz beaker with an inside diameter of approx 8 5 cm 3 1 2 in and made of an electrically non conductive material such as glass or plastic The placing of this standard load in the...

Страница 3: ... The following symptoms indicate a defective keyboard unit When touching the pads a certain pad produces no signal at all When touching a number pad two figures or more are displayed When touching the pads sometimes a pad produces no signal If The Keyboard Unit is Defective 1 Disconnect the power supply cord and then remove covers 2 Open the drawer and block it open 3 Discharge high voltage capaci...

Страница 4: ...ch stop switch operates properly that is the contacts are closed when the drawer is closed and open when the drawer is open If the door sensing switch stop switch is good disconnect the flat ribbon cable that connects the key unit to the control unit and make sure the drawer sensing switch is closed either close the drawer or short the door sensing switch connecter Use the Key unit matrix indicate...

Страница 5: ...hese relays are operated by D C voltage Check voltage at the relay coil with a D C voltmeter during the microwave cooking operation DC voltage indicated Defective relay DC voltage not indicated Check diode which is connected to the relay coil If diode is good control unit is defective COMPONENT TEST PROCEDURE LETTER RELAY SYMBOL OPERATIONAL VOLTAGE CONNECTED COMPONENTS RY1 Approx 26 vdc Oven lamp ...

Страница 6: ...n the oven cavity 2 Close the drawer touch the Defrost pad Then select Steaks Chops by touch ing the number pad 2 And touch the number pad 5 Now weight 0 5lb is set And then touch the start pad 3 The oven is in Defrost cooking condition 4 The oven will operate as follows WEIGHT 1ST STAGE 2ND STAGE 3RD STAGE LEVEL TIME LEVEL TIME LEVEL TIME 0 5 lb 60 20 sec 40 20 sec 30 45 sec 5 If improper operati...

Страница 7: ...he troubleshooting guide given below if indicator does not light up after above check and repairs are finished Disconnect the power supply cord Remove the outer case cabinet Open the door and block it open Discharge high voltage capacitor Disconnect the leads to the primary of the power transformer Ensure that these leads remain isolated from other components and oven chassis by using insulation t...

Страница 8: ...olvents near the oven while using Sensor settings The sensor will detect the vapor given of by the spray and turn off before food is properly cooked 8 If the sensor has not detected the vapor of the food ERROR will appear and the oven will shut off Water Load Cooking Test Make sure the oven has been plugged in at least two minutes before checking sensor cook operation The cabinet should be install...

Страница 9: ...If new sensor does not operate properly the problem is with the control unit and refer to explanation be low CHECKING CONTROL UNIT 1 Disconnect the power supply cord and then disassemble as per Drawer Microwave Disassembly Section 4 Component Access Removal Page 4 6 2 Open the drawer and block it open 3 Discharge high voltage capacitor 4 Disconnect the sensor connector that is mounted to control p...

Страница 10: ... Plunger NC NO COM COM NO NC R3 R4 R1 R2 1 2 3 F 1 F 2 F 3 To connector F on Control Unit CONNECTOR Refer to the Disassembly instructions found on page 16 G MAGNETRON ASSEMBLY TEST 1 Disconnect the power supply cord 2 Open the drawer and keep it open 3 To discharge high voltage capacitor wait for 60 seconds 4 To test for an open filament isolate the magnetron from the high voltage cir cuit A conti...

Страница 11: ...d the temperature of the water 2 Place the cup of water in the oven Operate oven at POWER 10 HIGH selecting more than 60 seconds cook time Allow the water to heat for 60 seconds measuring with a stop watch second hand of a watch or the digital read out countdown 3 Remove the cup from the oven and again measure the temperature making sure to stir the thermometer or thermocouple through the water un...

Страница 12: ...rd 2 Open the drawer and keep it open 3 To discharge high voltage capacitor wait for 60 seconds 4 Isolate the switch and connect the ohmmeter to the common COM and nor mally open NO terminal of the switch The meter should indicate an open circuit with the drawer open and a closed circuit with the drawer closed If improper operation is indicated replace the secondary interlock switch 5 Reconnect al...

Страница 13: ...a closed circuit When the monitor switch actuator is pushed by a screw driver through the lower latch hole on the front plate of the oven cavity with the drawer opened in this condition the plunger of the monitor switch is pushed in the meter should indicate an open circuit If improper operation is indicated the switch may be defective and both the monitor switch plus fuse will need to be replaced...

Страница 14: ...itor switch must be replaced with monitor fuse and monitor switch assembly See Section 5 even if the monitor switch operates normally The monitor fuse and monitor switch assembly is comprised of a 20 ampere fuse and switch 5 Reconnect all leads removed from components during testing 6 Reassemble the unit 7 Reconnect the power supply cord 8 Run the oven and check all functions M POWER TRANSFORMER T...

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