Duke DSO 500 Service Manual

SPEED OVEN

MODEL DSO 500

Service Manual

Please read this manual completely before attempting to

install, operate or service this equipment

Reproduction without written permission is prohibited. Duke is a registered

trademark of the Duke Manufacturing Company.

Duke Manufacturing Company

2305 N. Broadway

St. Louis, MO 63102

Phone: 314-231-1130

Toll Free: 1-800-735-3853

Fax: 314-231-5074

www.dukemfg.com

P/N 168465B

Service Manual for Speed Oven Model DSO 500

SAFETY PRECAUTIONS

PRECAUTIONS TO BE OBSERVED BEFORE AND DURING SERVICING TO AVOID POSSIBLE

EXPOSURE TO EXCESSIVE MICROWAVE ENERGY

(a) Do not operate or allow the oven to be operated with the door open.

(b) Make the following safety checks on all ovens to be serviced before activating the magnetron

or other microwave source, and make repairs as necessary.

(1) interlock operation

(2) proper door closing

(3) seal and sealing surfaces (arcing, wear, and other damage)

(4) damage to or loosening of hinges and latches

(5) evidence of dropping or abuse

generating compartments, check the magnetron, wave guide or transmission line, and cavity for proper alignment, integrity, and connections.

(d) Any defective or misadjusted components in the interlock monitor, door seal, and microwave

generation and transmission systems shall be repaired, replaced, or adjusted by procedures described in this manual before the oven is released to the owner.

(e) A microwave leakage check to verify compliance with the Federal Performance Standard should

be performed on each oven prior to release to the owner.

CAUTION: When servicing the unit, be sure no electrical wires contact a sharp edge.

Check all wiring for possible cuts and/or abrasions, which can occur during servicing.

Service Manual for Speed Oven Model DSO 500

TABLE OF CONTENTS

SAFETY PRECAUTIONS ....................................................................................................................3

INTRODUCTION .................................................................................................................................6

MAIN FEATURES ..........................................................................................................................7

INSTALLATION ...................................................................................................................................8

UNPACKING OVEN ......................................................................................................................8

RADIO INTERFERENCE ..............................................................................................................8

OVEN PLACEMENT......................................................................................................................8

ELECTRICAL INFORMATION .......................................................................................................8

EARTHING INSTRUCTIONS ........................................................................................................9

EXTERNAL EQUIPOTENTIAL ......................................................................................................9

SPECIFICATIONS .............................................................................................................................10

INPUT POWER ...........................................................................................................................10

OUTPUT POWER .......................................................................................................................10

DIMENSIONS ..............................................................................................................................10

WEIGHT ......................................................................................................................................10

RECOMMENDED CLEARANCES ..............................................................................................10

INTERNAL COOKING CAVITY DIMENSIONS............................................................................10

PREVENTIVE MAINTENANCE .........................................................................................................11

CLEANING ..................................................................................................................................11

SERVICING PROCEDURES ............................................................................................................12

GENERAL ....................................................................................................................................12

COMPONENT OVERVIEW ...............................................................................................................13

STIRRER MOTOR AND GEARBOX ...........................................................................................13

HIGH VOLTAGE TRANSFORMERS ...........................................................................................15

HIGH VOLTAGE RECTIFIERS ....................................................................................................17

HIGH VOLTAGE CAPACITORS ..................................................................................................19

MAGNETRONS ...........................................................................................................................21

MAGNETRON THERMAL SWITCHES .......................................................................................23

SOLID STATE RELAYS ...............................................................................................................25

MECHANICAL RELAYS AND INTERLOCK SWITCHES ............................................................27

HEATERS AND THERMAL CUTOUTS .......................................................................................29

LINE FUSES ................................................................................................................................31

JET PLATES ................................................................................................................................33

CABINET COOLING FANS .........................................................................................................35

TABLE OF CONTENTS

MAGNETRON COOLING FANS .................................................................................................37

CABINET THERMAL SWITCH ....................................................................................................39

KEYPAD/CONTROL BOARD ......................................................................................................41

INVERTERS ................................................................................................................................43

SYSTEM TESTING ...........................................................................................................................45

POWER OUTPUT MEASUREMENT ..........................................................................................45

MICROWAVE LEAKAGE TEST ...................................................................................................45

COMPONENT TESTING ...................................................................................................................47

POWER TRANSFORMER TEST ................................................................................................47

DISCHARGING THE HIGH VOLTAGE SYSTEM ON THE DUKE SPEED OVEN. .....................48

HIGH VOLTAGE CAPACITOR TEST ..........................................................................................49

HIGH VOLTAGE RECTIFIER TEST ............................................................................................50

MECHANICAL RELAYS AND INTERLOCK SWITCHES ............................................................51

REPAIR PROCEDURES ...................................................................................................................53

RELAY AND SWITCH REPLACEMENT ......................................................................................53

LINE FUSE REPLACEMENT ......................................................................................................54

INVERTER REPLACEMENT .......................................................................................................55

BLOWER MOTOR REPLACEMENT ...........................................................................................56

ELECTRICAL PANEL REPLACEMENT ......................................................................................58

MAGNETRON REPLACEMENT .................................................................................................59

STIRRER MOTOR REPLACEMENT ...........................................................................................60

HEATER ELEMENT REPLACEMENT ........................................................................................61

CABINET THERMAL SWITCH REPLACEMENT ........................................................................62

HIGH VOLTAGE TRANSFORMER REPLACEMENT..................................................................63

FRONT THERMAL COOLING FAN REPLACEMENT .................................................................64

INTAKE AND EXHAUST FANS REPLACEMENT .......................................................................65

ADJUSTMENTS ..........................................................................................................................66

TROUBLESHOOTING ......................................................................................................................67

SCHEMATIC DIAGRAM ....................................................................................................................71

SPARE PARTS LIST .........................................................................................................................72

APPENDIX A INVERTER PROGRAMMING .....................................................................................73

PROGRAMMING PROCEDURE .................................................................................................73

INVERTER SETTINGS................................................................................................................74

Service Manual for Speed Oven Model DSO 500

INTRODUCTION

512 10

1012 63 4

8 911

Figure 1

EQUIPMENT OVERVIEW

MAIN FEATURES

The main features of the Model DSO 500 Speed Oven are identied in Figure 1 and described below.

1. ON/OFF SWITCH

Turning ON the power switch will operate the blower fans, stirrer motor and cooling system. It will also activate the control panel and heat up the oven to the temperature setting, which will display “Oven Ready.

NOTE: When the Power Switch is turned “OFF”,

the rear mounted Cooling Fans will be running until the unit has cooled down or the power cord removed.

2. CONTROL PANEL

This is the electronic control board that is programmable for different menus, temperature setting, variable fan speed, Microwave Power Connection only, Microwave and Convection Combination, etc. This also has some service diagnostics.

3. DRAIN PAN

This serves as the collector of any liquid from the Oven cavity during cooking or cleaning.

4. OVEN CAVITY

The oven cavity is constructed from stainless steel and must be kept clean. (See CARE and CLEANING instructions in the OPERATOR’S MANUAL). The top cavity has a thin jet plate and the bottom cavity has the wire rack and bottom jet plate. A drain plug is also provided for ease of cleaning.

5. CONVECTION FAN

The unit has two blower systems (Top and Bottom) for distributing the patented impingement air system. Both blower systems can be operated independently over the entire speed range for more precise control of cooking, browning, etc. The perforated rear panel and the bottom jet plates must be kept clean and free of debris. (See CARE and CLEANING instructions in the OPERATOR’S MANUAL).

6. DOOR AND HEAT SHIELD

The door is pulled downwards and towards you to open. The door is designed with interlocks for microwave safety. The door should NOT be used to support heavy dishes. It must be kept clean. The door includes a heat shield attached to the front.(See CARE and CLEANING instructions in the OPERATOR’S MANUAL).

7. DOOR SEAL

These ensure a seal around the door cavity. They should be kept clean and checked regularly for signs of damage.

8. REMOVABLE BOTTOM JET PLATE

The bottom jet plate directs the air from the bottom of the oven to the underside of the product.

9. DRAIN OUTLET AND PLUG

Remove drain plug when cleaning. (See CARE and CLEANING instructions in the OPERATOR’S MANUAL). Make sure it is replaced into position before replacing bottom jet plate.

10. AIR OUTLETS

These air outlets and louvers on the left side, right side and rear panels are part of the cooling system of the electrical components. They must be kept free from obstruction. It will not allow microwave energy to escape into the environment. See clearance allowances specied in the INSTALLATION Section of this manual.

11. EXHAUST VENT

The exhaust vent is at the rear of the oven. This enables steam to escape and prevents build up of condensation. It will not allow microwave energy to escape into the environment.

12. COOLING FANS

Cooling Fans above the power cord are mounted to bring in cool air from the room into the machinery compartment. The single fan below the exhaust vent is directed to blow out the air from the machinery compartment.

Service Manual for Speed Oven Model DSO 500

INSTALLATION

UNPACKING OVEN

• Inspect oven for damage such as dents in door or inside oven cavity.

• Report any dents or breakage to source of purchase immediately. Do not attempt to use oven if damaged.

• Remove all materials from oven interior.

• If oven has been stored in extremely cold area, wait a few hours before connecting power.

RADIO INTERFERENCE

Microwave operation may cause interference to radio, television, or similar oven. Reduce or eliminate interference by doing the following:

• Clean door and sealing surfaces of oven according to instructions in Care and Cleaning instruction in the OPERATORS MANUAL

A. Allow at least 3” (7.62 cm) of clearance

around the sides of oven. Proper airow around the oven cools electrical components. With restricted airow, the oven may not operate properly and the life of electrical parts is reduced.

B. Install oven so oven bottom is at least 3

feet (91.5 cm) above oor.

• Place radio, television, etc. as far as possible from oven

• Use a properly installed antenna on radio, television, etc. to obtain stronger signal reception

OVEN PLACEMENT

• Do not install oven next to or above source

of heat, such as pizza oven or deep fat fryer. This could cause microwave oven to operate improperly and could shorten life of electrical parts

• Install oven on level countertop surface

• If provided, place warning label in a conspicuous place close to microwave oven

• Outlet should be located so that plug is accessible when oven is in place

• Provide clearance as shown in Figure 2 and described in the following paragraphs “A” and “B”

Figure 2. Oven Clearance Dimensions

ELECTRICAL INFORMATION

The switching operation of this microwave oven can cause voltage uctuations on the supply line. The operation of this oven under unfavorable voltage supply conditions can have adverse effects. This device is intended for the connection to a power supply system with maximum permissible system impedance Zmax of 1.1 Ohm at the interface point of the user’s supply. The user has to ensure that this device is connected only to a power supply system, which fullls the requirement above, If necessary, the user can ask the public power supply company for the system impedance at the interface point. The circuit breakers used in this oven are Type C.

EQUIPMENT OVERVIEW

WARNING

TO AVOID RISK OF ELECTRICAL SHOCK OR DEATH, THIS OVEN MUST BE GROUNDED AND PLUG MUST NOT BE ALTERED.

WARNING

IMPROPER USE OF THE GROUNDING CAN RESULT IN RISK OF ELECTRICAL SHOCK.” CONSULT A QUALIFIED ELECTRICIAN OR SERVICEMAN. IF THE GROUNDING INSTRUCTIONS ARE NOT COMPLETELY UNDERSTOOD, OR IF DOUBT EXISTS AS TO WHETHER THE APPLIANCE IS PROPERLY GROUNDED, AND “DO NOT USE AN EXTENSION CORD. IF THE POWER SUPPLY CORD IS TOO SHORT, HAVE A QUALIFIED ELECTRICIAN OR SERVICEMAN INSTALL AN OUTLET NEAR THE APPLIANCE.

If the product power cord is too short, have a qualied electrician install a three-slot receptacle. This oven should be plugged into a separate circuit with the electrical rating as provided in product specifications (available on Duke’s Wavelink website).

EXTERNAL EQUIPOTENTIAL

Earthing Terminal (export only)

Equipment has secondary earthing terminal. Terminal provides external earthing connection used in addition to earthing prong on plug. Located on outside of oven back, terminal is marked with this symbol.

WARNING

EARTHING INSTRUCTIONS

WARNING

OVEN MUST BE GROUNDED.

Grounding reduces risk of electric shock by providing an escape wire for the electric current if an electrical short occurs. This oven is equipped with a cord having a grounding wire with a grounding plug. The plug must be plugged into an outlet that is properly installed and grounded.

Consult a qualied electrician or service provider if grounding instructions are not completely understood, or if doubt exists as to whether the oven is properly grounded.

CAUTION: Do not use an extension cord.

DO NOT R EMOVE EARTHING PRONG WHEN INSTALLING EARTHED APPLIANCE IN A LOCATION THAT DOES NOT HAVE THREE WIRE EARTHING RECEPTACLE, UNDER NO C ONDITION IS EARTHING PRONG TO BE CUT OFF OR REMOVED. IT IS THE PERSONAL RESPONSIBILITY OF THE EQUIPMENT OWNER TO CONTACT A QUALIFIED ELECTRICIAN AND HAVE PROPERLY EARTHED THREE PRONG WALL RECEPTACLE INSTALLED IN ACCORDANCE WITH APPROPRIATE ELECTRICAL CODES.

Wire Color Code

The standard accepted color coding for earthing wires is Green or green with a yellow strip.

WARNING

EARTHING LEADS ARE NOT INTENDED TO CARRY CURRENT IN NORMAL OPERATION.

The service technician must replace all earths prior to completion of the service call. Under no condition should earth wire be left off causing a potential hazard to service technicians and consumer.

Service Manual for Speed Oven Model DSO 500

SPECIFICATIONS

Table 2 lists the specications for the Model DSO 500 Speed Oven.

Table 2. Specications

MODEL NO. DSO 500

INPUT POWER

Operating Voltage 208 – 240 VAC, 60 Hz Current 29 Amps Phase Single Circuit Breaker 30A, Type C or D

OUTPUT POWER

Microwave 1600 Watts Heaters 5400 Watts

DIMENSIONS

Height 26 in. (with 4 in. legs) Width 25 7/8 in. Depth 31 in. (incl. door handle)

WEIGHT

Unpacked Approximately 250 lbs. Packed 360 lbs.

RECOMMENDED CLEARANCES

Height None required Width 3 inches on each side Depth None required

INTERNAL COOKING CAVITY DIMENSIONS

Height 8 in. Width 16 in. Depth 14-1/2 in.

PREVENTIVE MAINTENANCE

EQUIPMENT OVERVIEW

CLEANING

Stainless Steel Care and Cleaning

To prevent discoloration or rust on stainless steel several important steps need to be taken. First, we need to understand the properties of stainless steel. Stainless steel contains 70-80% iron which will rust. It also contains 12-20% chromium which forms an invisible passive lm over the steels surface which acts as a shield against corrosion. As long as the protective layer is intact, the metal will not corrode. If the lm is broken or contaminated, outside elements can begin to breakdown the steel and begin to form rust or discoloration.

Proper cleaning of stainless steel requires soft cloths or plastic scouring pads.

CAUTION: Never use steel pads, wire brushes

or scrapers.

Early signs of stainless steel breakdown can consist of small pits and cracks. If this has begun, clean thoroughly and start to apply stainless steel cleaners in attempt to restore the passivity of the steel.

WARNING

THE POWER MUST BE TURNED OFF AND POWER CORD DISCONNECTED WHENEVER PERFORMING MAINTENANCE OR REPAIR FUNCTIONS.

Gasket Maintenance

Gaskets require regular cleaning. Gasket cleaning can be done with the use of warm soapy water. Also, never use sharp tools or knives to scrape or clean the gasket which could possibly damager the gasket.

Cleaning solutions need to be alkaline based or non-chloride cleaners. Any cleaner containing chlorides will damage the protective lm of the stainless steel. Chlorides are also commonly found in hard water, salts and household and industrial cleaners. If cleaners containing chlorides are used, be sure to rinse repeatedly and dry thoroughly upon completion.

Routine cleaning of stainless steel can be done with soap and water. Extreme stains or grease should be cleaned with a non-abrasive cleaner and plastic scrub pad. It is always good to rub with the grain of the steel. There are also stainless steel cleaners available which can restore and preserve the nish of the steels protective layer.

Service Manual for Speed Oven Model DSO 500

SERVICING PROCEDURES

GENERAL

The service section of this manual includes a section called component overview. Information on each component is a separate page. This overview is not intended to provide detailed information. Its purpose is to provide a general understanding of what the component does and how it is tested and replaced. When a procedure is to be performed, refer to the detailed REPAIR PROCEDURES. The information in this overview includes the following:

• A general description of the function of the component in the oven operation

• Location and Access information

• Safety Issues

• Tools Required

• Operational Testing

• Test Procedure

• Replacement Procedure

NOTE: Remember this overview is only intended

to provide a brief discussion on each component. Details for testing, adjusting and replacement are provided separately in the TESTING and REPAIR section of this manual and should be referred to when performing any procedure.

In addition to the Overview section this chapter includes the following:

• Power Output Measurement

• Microwave Leakage Test

• Component Detailed Testing

• Detai l ed Re p air an d Re p l acement Procedures

• Adjustment Procedures

• Troubleshooting Procedures

Additional chapters provide the Schematic Diagram and the Spare Parts list.

COMPONENT OVERVIEW

STIRRER MOTOR AND GEARBOX

The stirrer motor and gearbox, Figure 3, is located near the front of the oven upper chamber above the upper jetplate. The stirrer motor rotates the stirrer blade at 20 rpm. The rotating stirrer blade evenly distributes the microwave eld and the upper hot airow into the cook chamber to ensure uniformity. Should the stirrer blade cease to rotate during cooking, severe nonuniformity of cooking will be observed. Localized burning of the food may occur and in the case of cooking frozen food, very cold uncooked areas may be detected.

Location and access

The stirrer motor is centrally located above the top of the cook chamber. The top and side panels will need to be removed.

Surface Components

Safety issues

• Electrical supply of 208/240 VAC to stirrer

motor which becomes live when power cord is live

• Proximity to High Voltage system (5

kVDC) which can remain live, even after power down

• Upper end of motor shaft rotates rapidly

with small exposed cooling fan

Tools required

• Flat blade screwdriver to remove top and

side panels

• 11/32 inch nut driver to remove nuts se-

curing motor and gearbox to top of oven

• Voltmeter

• Flash light

Operational testing

The stirrer motor is powered from the 208/240 VAC mains supply and is not controlled from the main on/off switch on the right hand side. The door safety interlocks interrupt this supply when the door is opened, so that the stirrer blade is stationary whenever the door is opened. The interlock function should be checked by opening and closing the cook door and observing the rotation of the stirrer motor fan. The rotation of the stirrer blade can be checked by removing the upper jet plate or observing the position of the stirrer blade through the air holes in the upper jet plate with a ashlight.

Figure 3. High Voltage and Inside Top

Service Manual for Speed Oven Model DSO 500

Test procedure

Check 208/240 VAC is present on the motor power connections, wires 47 and 49, as above.

If power is not present, check incoming line voltage, line fuses, mechanical relays K6, K8 and primary and secondary door switches.

If power is present at all times, the door interlock safety system has failed. Check the mechanical relays K6, K8 and primary and secondary door switches.

STIRRER MOTOR AND GEARBOX - NOTES

Replacement

After removing the side and top panels and disconnecting the power cord, the stirrer motor power leads can be disconnected. There are four 11/32 inch nuts securing the stirrer motor and gearbox. Upon retting, align the dnveshaft of the gearbox with the head of the coupling to the stirrer blade.

COMPONENT OVERVIEW

HIGH VOLTAGE TRANSFORMERS

The transformers, Figure 4, step up the input line voltage to 2.5 kV. This voltage is rectied by the high voltage diodes and the high voltage capacitors for operation of the magnetrons.

Location and Access

The transformers are centrally located above the top of the cook chamber. The top and side panels will need to be removed.

Safety Issues

WARNING

THE HIGH VOLTAGE CAPACITORS RETAINS THE 2.5 kVDC CHARGE EVEN AFTER THE OVEN IS DISCONNECTED. THIS CAPACITOR MUST BE DISCHARGED BEFORE WORKING ON ANY COMPONENTS IN THE HIGH VOLTAGE AREA.

• Electrical supply of 208/240 VAC to trans-

formers when POWER switch is in ON position and oven doors are closed

Tools Required.

• Flat blade screwdriver to remove top and

side panels

• 3/8 inch nut driver to remove nuts secur-

ing transformers to top of oven

• Voltmeter

Figure 4. High Voltage Transformers

Operational Testing.

The transformers are powered from the 208/240 VAC mains supply through solid state relays K4 and K5 and mechanical relay K6 and K8. Relays K6 and K8 are controlled by the door safety interlock requiring the oven door to be closed to provide primary voltage to the transformers. The door safety interlocks interrupt this supply when the door is opened. Operation of relays K4 and K5 required the POWER switch to be in the ON position to provide operating voltage to the control board. The interlock function can be checked by opening and closing the oven door and observing the rotation of the blade on top of the stirrer motor.

Service Manual for Speed Oven Model DSO 500

Test Procedure

WARNING

HIGH VOLTAGE CAPACITOR MUST BE DISCHARGED BEFORE SERVICING. REFER TO DETAILED PROCEDURE IN THE COMPONENT TESTING SECTION BEFORE TESTING.

NOTE: Dangerous voltages can be present at

this component. Refer to detailed test procedure for testing this component.

Check 208/240 VAC is present on the transformer primaries, wires 26 and 45 for mag #1 transformers and wires 27 and 48 for mag #2 transformer.

If power is not present, check incoming line voltage, line fuses, mechanical relays K6, K8 and primary and secondary door switches.

Replacement

WARNING

THE HIGH VOLTAGE CAPACITOR RETAINS THE 2.5 kVDC CHARGE EVEN AFTER THE OVEN IS DISCONNECTED. THIS CAPACITOR MUST BE DISCHARGED BEFORE WORKING ON ANY COMPONENTS IN THE HIGH VOLTAGE AREA.

After removing the side and top panels and disconnecting the power cord, the transformer primary and secondary leads can be disconnected. There are four 3/8 inch nuts securing the transformers.

If power is present at all times, the door interlock safety system has failed. Check the mechanical relays K6, K8 and primary and secondary door switches and POWER ON/OFF switch.

HIGH VOLTAGE TRANSFORMERS - NOTES

COMPONENT OVERVIEW

HIGH VOLTAGE RECTIFIERS

The high voltage diodes, Figure 5, rectify the incoming 2.5 kV voltage and doubles it providing 5kVDC for magnetron operation.

Location and Access

The diodes are located above the top of the cook chamber at the rear of the oven. The top and side panels will need to be removed.

Safety Issues

WARNING

THE HIGH VOLTAGE CAPACITOR RETAINS THE 2.5 kVDC CHARGE EVEN AFTER THE OVEN IS DISCONNECTED. THIS CAPACITOR MUST BE DISCHARGED BEFORE WORKING ON ANY COMPONENTS IN THE HIGH VOLTAGE AREA.

• Electrical supply of 208/240 VAC to trans-

formers when POWER switch is in ON position and oven doors are closed

Tools Required

• Flat blade screwdriver to remove top and

side panels

• Phillips #2 screwdriver to remove screws

securing diodes to top of oven

• Ohmmeter to check diodes

Figure 5. High Voltage Rectiers

Operational Testing

The transformers connected to the diodes are powered from the 208/240 VAC mains supply through solid state relays K4 and K5 and mechanical relay K6 and K8. Relays K6 and K8 are controlled by the door safety interlock requiring the oven door to be closed to provide primary voltage to the transformers. The door safety interlocks interrupt this supply when the door is opened. Operation of relays K4 and K5 require the POWER switch to be in the ON position to provide operating voltage to the control board. The interlock function can be checked by opening and closing the oven door and observing the rotation of the blade on top of the stirrer motor.

Service Manual for Speed Oven Model DSO 500

Test Procedure

WARNING

HIGH VOLTAGE CAPACITOR MUST BE DISCHARGED BEFORE SERVICING. REFER TO DETAILED PROCEDURE IN THE COMPONENT TESTING SECTION BEFORE TESTING.

NOTE: Dangerous voltages can be present at

this component. Refer to detailed test procedure for testing this component.

Disconnect the wires to the diodes. Use an ohmmeter to check diodes. Diodes should conduct in one direction showing low resistance and not conduct in the reverse direction, thus indicating a very high resistance. High or low resistance in both directions indicates a defective diode.

HIGH VOLTAGE RECTIFIERS - NOTES

Replacement

WARNING

HIGH VOLTAGE CAPACITOR MUST BE DISCHARGED BEFORE SERVICING THE TRANSFORMERS

After removing the side and top panels and disconnecting the power cord, the diode leads can be disconnected. There are two screws securing each diode.

COMPONENT OVERVIEW

HIGH VOLTAGE CAPACITORS

The high voltage capacitors, Figure 6, store the rectied high voltage (2.5 kVDC) for operation of the magnetrons.

Location and Access.

The capacitors are located above the top of the cook chamber at the rear of the oven. The top and side panels will need to be removed.

Safety Issues

WARNING

THE HIGH VOLTAGE CAPACITOR RETAINS THE 2.5 kVDC CHARGE EVEN AFTER THE OVEN IS DISCONNECTED. THIS CAPACITOR MUST BE DISCHARGED BEFORE WORKING ON ANY COMPONENTS IN THE HIGH VOLTAGE AREA.

• Electrical supply of 208/240 VAC to trans-

formers when POWER switch is in ON position and oven doors are closed

• Capacitors charge to the 2.5 kVDC level

when the high voltage circuit is properly operating

Tools Required

• Flat blade screwdriver to remove top and

side panels

Figure 6. High Voltage Capacitors

• 5/16 inch nut driver to remove nuts secur-

ing diodes to top of oven

• Ohmmeter to check capacitors

Operational Testing

The capacitors charge whenever the transformer is operating. The transformers connected to the diodes for charging the capacitors are powered from the 208/240 VAC mains supply through solid state relays K4 and K5 and mechanical relay K6 and K8. Relays K6 and K8 are controlled by the door safety interlock requiring the oven door to be closed to provide primary voltage to the transformers. The door safety interlocks interrupt this supply when the door is opened. Operation of relays K4 and K5 require the POWER switch to be in the ON position to provide operating voltage to the control board. The interlock function can be checked by opening and closing the oven door and observing the rotation of the fan on top of the stirrer motor.

Service Manual for Speed Oven Model DSO 500

Test Procedure

WARNING

HIGH VOLTAGE CAPACITOR MUST BE DISCHARGED BEFORE SERVICING. REFER TO DETAILED PROCEDURE IN THE COMPONENT TESTING SECTION BEFORE TESTING.

NOTE: Dangerous voltages can be present at

this component. Refer to detailed test procedure for testing this component.

HIGH VOLTAGE CAPACITORS - NOTES

Replacement

WARNING

HIGH VOLTAGE CAPACITOR MUST BE DISCHARGED BEFORE REPLACEMENT.

Capacitor must be discharged before removal. After discharging, disconnect leads. There are two nuts securing the capacitor bracket.

COMPONENT OVERVIEW

MAGNETRONS

The magnetron filament voltage of 4.5 VAC is supplied from the high voltage transformer lament winding. The operating voltage of 5000 VDC is provided by the rectied output from the transformer high voltage winding.

Location and Access

The magnetrons, Figure 7, are located above the top of the cook chamber at the left and right side of the oven. The top and side panels will need to be removed.

Safety Issues

WARNING

THE HIGH VOLTAGE CAPACITOR RETAINS THE 2.5 kVDC CHARGE EVEN AFTER THE OVEN IS DISCONNECTED. THIS CAPACITOR MUST BE DISCHARGED BEFORE WORKING ON ANY COMPONENTS IN THE HIGH VOLTAGE AREA.

• Electrical supply of 208/240 VAC to trans-

formers when POWER switch is in ON position and oven doors are closed

• Capacitors charge to the 2.5 kVDC level

when the high voltage circuit is properly operating

• The 4.5 VAC magnetron lament supply

is at 2500 V relative to the chassis

Tools required

Figure 7. Magnetrons

• Flat blade screwdriver to remove top and

side panels

• 3/8 inch nut driver to remove nuts secur-

ing the magnetrons to top of oven

Operational Testing.

The magnetrons receive lament and high voltage from the high voltage transformers. The transformers connected to the diodes for charging the capacitors are powered from the 208/240 VAC mains supply through solid state relays K4 and K5 and mechanical relay K6 and K8. Relays K6 and K8 are controlled by the door safety interlock requiring the oven door to be closed to provide primary voltage to the transformers. The door safety interlocks interrupt this supply when the door is opened. Operation of relays K4 and K5 require the POWER switch to be in the ON position to provide operating voltage to the control board. The interlock function can be checked by opening and closing the oven door and observing the rotation of the blade on top of the stirrer motor.

Service Manual for Speed Oven Model DSO 500

Test Procedure

WARNING

HIGH VOLTAGE CAPACITOR MUST BE DISCHARGED BEFORE SERVICING. REFER TO DETAILED PROCEDURE IN THE COMPONENT TESTING SECTION BEFORE TESTING.

NOTE: Dangerous voltages can be present at

this component. Refer to detailed test procedure for testing this component.

MAGNETRONS - NOTES

Replacement

WARNING

HIGH VOLTAGE CAPACITOR MUST BE DISC H ARGED BEFORE M AGNETRON REPLACEMENT.

Remove cooling duct. (Right side magnetron only). Label and disconnect wires from transformer to magnetron lament. Disconnect wires to thermostat. Remove nuts attaching magnetron to top surface. When installing the new magnetron, be sure metal mesh gasket is properly positioned around the magnetron dipole antenna and that thermostat is installed on magnetron. Secure magnetron to top surface with nuts. Reconnect wires to lament and thermostat.

COMPONENT OVERVIEW

MAGNETRON THERMAL SWITCHES

The magnetron thermal switches, Figure 8, are used to monitor the magnetron temperature and open the high voltage supply when the temperature exceeds 150°C.

Location and Access

The magnetrons thermostats are located on the side of each magnetron. The top and side panels will need to be removed.

Safety Issues

WARNING

THE HIGH VOLTAGE CAPACITOR RETAINS THE 2.5 kVDC CHARGE EVEN AFTER THE OVEN IS DISCONNECTED. THIS CAPACITOR MUST BE DISCHARGED BEFORE WORKING ON ANY COMPONENTS IN THE HIGH VOLTAGE AREA.

• Electrical supply of 208/240 VAC to trans-

formers when POWER switch is in ON position and oven doors are closed

• Capacitors charge to the 2.5 kVDC level

when the high voltage circuit is properly operating

Tools required

• Flat blade screwdriver to remove top and

side panels

Figure 8. Magnetron Thermal Switches

• 3/8 inch nut driver to remove nuts secur-

ing the magnetrons to top of oven

Operational Testing

The thermostats are connected in the high voltage transformer primary circuit and are normally closed connecting primary voltage on wires 26 and 27 to the high voltage transformer. If magnetron is not operating check continuity across thermostat terminals.

Service Manual for Speed Oven Model DSO 500

Test Procedure

WARNING

HIGH VOLTAGE CAPACITOR MUST BE DISCHARGED BEFORE SERVICING. REFER TO DETAILED PROCEDURE IN THE COMPONENT TESTING SECTION BEFORE TESTING.

NOTE: Dangerous voltages can be present at

this component. Refer to detailed test procedure for testing this component.

NOTE: Disconnect wires to thermostat and check

continuity across thermostat terminals. Continuity should be indicated when thermostat is at normal ambient temperature.

MAGNETRON THERMAL SWITCHES - NOTES

Replacement

WARNING

HIGH VOLTAGE CAPACITOR MUST BE DISC H ARGED BEFORE M AGNETRON THERMOSTAT REPLACEMENT.

Label and disconnect wires to thermostat. Remove screw securing thermostat to magnetron and remove thermostat. When installing a new thermostat, secure with screw. Connect wires to thermostat.

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