Bosch HMV5053C User manual

All About
Servicing
OVER THE RANGE
MICROWAVE OVENS
HMV505U
HMV505C
This manual is designed to be used by qualified service personnel only.
Due to the complexity and the risk of high-voltage electrical shock,
Bosch does not recommend that customers service their own units.
This material is intended for the sole use of BSH authorized persons
and may contain confidential and proprietary information. Any
unauthorized review, use, copying, disclosure, or distribution in any
format is prohibited.

Section 1 Basic Information
1-1
Safe Servicing Practices
Avoid personal injury and/or property damage by observing important Safe Servicing Practices.
Following are some limited examples of safe practices:
1. DO NOT attempt a product repair if you have any doubts as to your ability to complete the repair in a safe and
satisfactory manner.
2. Always Use The Correct Replacement Parts as indicated in the parts documentation. Substitutions may defeat
compliance with Safety Standards Set For Home Appliances. Do not exceed maximum recommended wattage on
light bulb replacements. Doing so could blow fuses and/or damage transformers.
3. Before servicing or moving an appliance:
• Remove power cord from the electrical outlet, trip circuit breaker to the OFF position, or remove fuse.
4. Never interfere with the proper operation of any safety device.
5. Use ONLY REPLACEMENT PARTS CATALOGED FOR THIS APPLIANCE. Substitutions may defeat compliance with
Safety Standards Set For Home Appliances.
6. GROUNDING: The standard color coding for safety ground wires is GREEN, or GREEN with YELLOW STRIPES.
Ground leads are not to be used as current carrying conductors. It is EXTREMELY important that the service
technician reestablish all safety grounds prior to completion of service. Failure to do so will create a hazard.
7. Prior to returning the product to service, ensure that:
• All electrical connections are correct and secure.
• All electrical leads are properly dressed and secured away from sharp edges, high-temperature components,
and moving parts.
• All non-insulated electrical terminals, connectors, heaters, etc. are adequately spaced away from all metal
parts and panels.
• All safety grounds (both internal and external) are correctly and securely connected.
• All panels are properly and securely reassembled.

Section 1 Basic Information
1-2
Table of Contents
Section 1 Basic Information
Safe Servicing Practices........................................ 1-1
Table of Contents................................................. 1-2
Warnings and Safety Information.......................... 1-3
Precautions To Be Observed Before And During
Servicing To Avoid Possible Exposure To
Excessive Microwave Energy................................. 1-4
Before Servicing................................................... 1-4
Danger High Voltage ............................................ 1-4
Before Servicing................................................... 1-5
When Testing Is Completed.................................. 1-5
Microwave Measurement Procedure USA................ 1-6
Microwave Measurement Procedure Canada........... 1-7
Product Specification............................................ 1-8
Grounding Instructions......................................... 1-9
Electrical Requirements ........................................ 1-9
Oven Diagram...................................................... 1-10
Section 2 OperationSection 2 Operation
Operating Sequence Description............................ 2-1
Off Condition .................................................... 2-1
Cooking Condition............................................. 2-1
Ventilation Methods Hot Air Exhaust...................... 2-2
Power Level P-0 To P-90 Cooking.......................... 2-2
Oven Schematic-Off Condition............................... 2-3
Oven Schematic-Cooking Condition........................ 2-3
Touch Control Panel Assembly Outline................... 2-4
Component Descriptions....................................... 2-4
Door Open Mechanism ......................................... 2-4
Door Sensing And Primary Interlock Switch............ 2-4
Monitor Switch..................................................... 2-5
Thermal Cut-Out (Cavity)...................................... 2-5
Thermal Cut-Out (Hood)....................................... 2-5
Turntable Motor................................................... 2-5
Cooling Fan Motor................................................ 2-5
Hood Fan Motor................................................... 2-5
Hood Lamp.......................................................... 2-5
Section 3 Troubleshooting and Testing
Warnings and Cautions......................................... 3-1
Troubleshooting Guide Chart................................. 3-2
Test Procedures................................................... 3-3
Section 4 Component Teardown
Warnings and Cautions......................................... 4-1
Hood Exhaust Louver Removal.............................. 4-2
Removal Of Oven From Wall ................................. 4-2
Outer Case Removal............................................. 4-3
Power Transformer Removal................................. 4-3
High Voltage Rectifi er And High Voltage
Capacitor Removal ............................................... 4-4
Magnetron Removal ............................................. 4-4
Hood Fan Thermal Cut-Out Removal...................... 4-4
Hood Fan Motor Removal...................................... 4-5
Thermal Cut-Out (Cavity) Removal........................ 4-5
Cooling Fan Motor Removal .................................. 4-5
Turntable Motor And Food Lamp Sockets Removal.. 4-6
Oven Lamp And Lamp Socket Removal.................. 4-6
Servicing The Touch Control Panel ....................... 4-6
Control Panel Assembly, Control Unit And
Key Unit Removal................................................. 4-8
Door Sensing Switch, Primary Interlock
Switch And Monitor Switch Removal...................... 4-9
Door Sensing Switch, Primary Interlock
Switch, And Monitor Switch Adjustment................. 4-9
Door Replacement................................................ 4-10
Door Disassembly................................................. 4-11
.......... 4-12Humidity Sensor And Stirrer Motor Removal ..
This Manual has been prepared to provide Authorized Service Personnel with Operation and Service Information for
Fault Codes .................................................... 2-1
Bosch Microwave Hood Combination Models: HMV5053U, HMV5053C.

Certain in parts are intentionally not grounded and present a risk of electrical shock only during
servicing. Service personnel - do not contact the following parts while the appliance is energized:
Inverter unit, that includes high voltage capacitor, high voltage power transformer, high voltage
rectifier, heat sink, etc., magnetron, high voltage harness etc.; if provided, fan assembly, cooling fan
motor.
Removal of the outer wrapper gives access to voltage above 250v.
Section 1 Basic Information
1-3
WARNING
This service manual is intended for use by persons having electrical and mechanical training and a
level of knowledge of these subjects generally considered acceptable in the appliance repair trade.
BSH Home Appliances cannot be responsible, nor assume any liability, for injury or damage of
any kind arising from the use of this manual.
WARNING
Never operate the oven until the following points are ensured.
(A) The door is tightly closed.
(B) The door brackets and hinges are not defective.
(C) The door packing is not damaged.
(D) The door is not deformed or warped.
(E) There is no other visible damage with the oven.
Servicing and repair work must be carried out only by trained service personnel.
WARNING
ternal

Section 1 Basic Information
1-4
Precautions To Be Observed Before And During Servicing To Avoid Possible Exposure To
Excessive Microwave Energy
1. Do not operate or allow the oven to be operated with the door open.
2. Make the following safety checks on all ovens to be serviced before activating the magnetron or other micro
wave 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.
3. Before turning on microwave power for any service test or inspection within the microwave generating
compartments, check the magnetron, wave guide or transmission line, and cavity for proper alignment, integrity,
and connections.
4. 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.
5. A microwave leakage check to verify compliance with the Federal Performance Standard should be performed on
each oven prior to release to the owner.
Danger High Voltage
Do not energize a microwave oven with the outer case cabinet removed, because a microwave oven generates high
voltage in the circuit.
If you intend to operate the oven employing the high frequency switching power converter circuit, you should take
special precautions to avoid an electrical shock hazard.
The high voltage transformer, high voltage capacitor and high voltage diode have energized high voltage potential
of approximately 4KV.
The aluminium heat sink is connected to the switching power transistor collector pole, and has an energized high
voltage potential of approximately 650V peak.
DO NOT ACCESS THE HIGH VOLTAGE TRANSFORMER, HIGH VOLTAGE CAPACITOR, HIGH VOLTAGE DI-
ODE AND HEAT SINK WHEN THE POWER SUPPLY IS CONNECTED TO AN ELECTRICAL OUTLET.
Before Servicing
Before servicing an operative unit, perform a microwave emission check as per the Microwave Measurement
Procedure outlined in this service manual.
If microwave emissions level is in excess of the specified limit, contact Sears Home Service immediately.
If the unit operates with the door open, service person should:
1. Tell the user not to operate the oven.
2. Contact BOSCH Home Service and Food and Drug Administration’s Center for Devices and
Radiological Health immediately.
Service personnel should inform BSH Home Appliances of any certified unit found with emissions in
excess of 5mW/cm2. The owner of the unit should be instructed not to use the unit until the oven has been brought
into compliance.

Microwave ovens contain circuitry capable of producing
very high voltage and current. Contact with the
following parts may result in a severe, possibly fatal,
electrical shock.
High Voltage Power Transformer, High Voltage Rectifier,
Heat sink etc., and Magnetron, High Voltage Harness etc..
Read the Service Manual carefully and follow all
instructions.
WARNING
Section 1 Basic Information
1-5
Before Servicing
1. Disconnect the power supply cord, and thenremove
outer case.
2. Open the door and block it open.
3. Discharge high voltage capacitor.
Whenever troubleshooting is performed, the power
supply must be disconnected. It may, in some cases, be
necessary to connect the power supply after the outer
case has been removed, in this event:
1. Disconnect the oven power supply cord and then
remove the outer case.
2. Open the door and block it open.
3. Discharge high voltage capacitor.
5. Ensure that these leads remain isolated from other
components and oven chassis by using insulation
tape.
6. After that procedure, reconnect the power supply
cord.
When Testing Is Completed
1. Disconnect the power supply cord
.
2. Open the door and block it open.
3. Discharge high voltage capacitor.
5. Reinstall the outer case (cabinet).
6. Reconnect the power supply cord after the outer
case is installed.
7. Run the oven and check all functions.
After repairing
1. Reconnect all leads removed from components
during testing.
2. Reinstall the outer case (cabinet).
3. Reconnect the power supply cord after the outer
case is installed.
4. Run the oven and check all functions. Microwave
ovens should not be run empty. To test for the
presence of microwave energy within a cavity,
place a cup of cold water on the oven turntable,
close the door and set the power to HIGH and then
set the microwave timer for two (2) minutes. When
the two minutes has elapsed (timer at zero) care-
fully check that the water is now hot. If the water
remains cold carry out Before Servicing procedure
and re-examine the connections to the component
being tested.
Don't Touch!
Danger High
Voltage
To discharge the high voltage capacitor, wait for 60
seconds and then short-circuit the connection of the
high-voltage capacitor (that is the connecting lead of
the high-voltage rectifier) against the chassis with the
use of an insulated screwdriver.
NOTE To discharge the high voltage capacitor, wait for 60
seconds and then short-circuit the connection of the
high-voltage capacitor (that is the connecting lead of
the high-voltage rectifier) against the chassis with the
use of an insulated screwdriver.
NOTE
High Voltage Circuit, that includes High Voltage Capacitor,
4. Disconnect leads to the primary of the H.V.Transformer.
4. Reconnect leads to the primary of the H.V.Transformer.

Section 1 Basic Information
1-6
Microwave Measurement Procedure (USA)
A. Requirements:
1) Microwave leakage limit (Power density limit): The power density of microwave radiation emitted by a
microwave oven should not exceed 1 mW/cm2at any point 5 cm 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/cm2at any point 5 cm or more from the external surface of the oven.
2) Safety interlock switches: Primary interlock switch shall prevent microwave radiation emission in excess of the
requirement as above mentioned, secondary interlock switch shall prevent microwave radiation emission in
excess of 5 mW/cm2at any point 5 cm or more from the external surface of the oven.
B. 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.
Important:
Survey instruments that comply with the requirement for instrumentation as prescribed by the performance
standard for microwave ovens, 21 CFR 1003 1004, must be used for testing.
2) Place the oven tray in the oven cavity.
3) 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 nonconductive 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.
4) Set the cooking control on Full Power Cooking Mode.
5) Close the door 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.
C. Leakage test:
Closed-door leakage test (microwave measurement)
1) Grasp the probe of the survey instrument and hold it perpendicular to the gap between the door 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
indication on the meter.
3) Check for leakage at the door 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 door pull the door away from the front of the oven as far as is permitted 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
5 mW/cm2, and that the primary interlock switch and secondary interlock switch do turn the oven OFF before
any door movement.
NOTE: After servicing, record data on service invoice and microwave leakage report.
,

Section 1 Basic Information
1-7
Microwave Measurement Procedure (Canada)
After adjustment of the door switches are completed individually or collectively, switch test and microwave leakage test
must be performed with survey instrument and test result must be confirmed to meet the requirement of the
performance standard for microwave ovens as under mentioned.
A. Requirements:
Every microwave oven shall function in such a manner that when the oven is fully assembled and operating with
its service controls and user controls adjusted to yield the maximum output, the leakage radiation, at all points at
least 5 cm. from the external surface of the oven, does not exceed:
1) 1.0 mW/cm2with the test load of 275 ± 15 ml of water at an initial temperature 20 ±5°C.
2) 5.0 mW/cm2when the outer enclosure is removed with a test load of 275 ± 15 ml of water at an initial
temperature 20±5°C.
3) 5.0 mW/cm2without a test load.
B. 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.
Survey instruments that comply with the requirement for instrumentation as prescribed by CSA and NHW
performance standard for microwave ovens must be used for testing recommended instruments are, NARDA
8100 and NARDA 8200.
2) Place the oven tray in the oven cavity.
3) Place the load of 275±15 ml (9.8 oz) of tap water initially at 20°±5°C (68°F) in the center of oven cavity.
The water container shall be a low form of a 600 ml (20 oz) beaker with an inside diameter of approx. 8.5 cm
(3-1/2 in.) and made of an electrically nonconductive 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.
4) Set the cooking control on Full Power Cooking Mode.
5) Close the door 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.
C. Leakage test with enclosure installed:
1) Grasp probe of survey instrument and hold it perpendicular to gap between door and the body of the oven.
2) Move the probe slowly, not faster than 2.5 cm/sec. along the gap, watching for maximum indication on meter.
3) Check for leakage at the door screen, sheet metal seams and other accessible positions where continuity
of the metal has been breached (eg., around the switches, indicator, and vents). While testing for leakage
around door, pull door away from the front of the oven as far as is permitted 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 4 mW/cm2, and that the primary interlock switch and secondary interlock switch do turn the oven
OFF before any door movement.
D. Leakage test without enclosure:
1) Remove the enclosure (cabinet).
2) Grasp the probe of the survey instrument and hold it perpendicular to all mechanical and electric parts of the
oven that is accessible to the user of the oven including, but not limited to, the waveguide, cavity seams,
magnetron, as well as the gap between the door and the body of the oven.
3) Move probe slowly, not faster than 2.5 cm/sec. along the gap, watching for the maximum indication on meter.
4) Measure carefully at the point of highest leakage and make sure that the highest leakage is under 5 mW/cm2.
CAUTION: Special attention should be given to avoid electrical shock because HIGH VOLTAGE is
generated during this test.
NOTE: After servicing, record data on service invoice and microwave leakage report.

Section 1 Basic Information
1-8
Product Specification
Item Description
Power Requirements
60 Hertz
Single phase, 3 wire grounded
Power Output
Operating frequency of 2450MHz
Case Dimensions (excluding handle)
Cooking Cavity Dimensions
(2.1 Cubic Feet )
Hood Lamp 2 bulbs, 30W x 2, Incandescent light bulbs
Hood fan
Control Complement Touch Control System
Clock ( 1:00 - 12:59 )
Timer (0 - 99 min. 99 seconds)
Microwave Power for Variable Cooking
Repetition Rate;
P-HI Full power throughout the cooking time
P-90 approx. 90% of Full Power
P-80 approx. 80% of Full Power
P-70 approx. 70% of Full Power
P-60 approx. 60% of Full Power
P-50 approx. 50% of Full Power
P-40 approx. 40% of Full Power
P-30 approx. 30% of Full Power
P-20 approx. 20% of Full Power
P-10 approx. 10% of Full Power
Oven Cavity Light
Safety Standard UL Listed FCC Authorized
DHHS Rules, CFR, Title 21, Chapter 1, Subchapter J
Canadian Standards Association
Health CANADA, Industry Canada
Weight
(USA)120 Volts / 14.8 Amperes, 1650 Watts
Approx. 62.2lbs
Width 29.88
” Height 17.56” Depth 17.06”
Width 21.25”
Height 9.94”
Depth 14.72”
1 0 watts (IEC 705 Test Procedure)10
Approx. 400 C.F.M (Turbo mode)
Approx. 300 C.F.M (High mode)
Approx. 200 C.F.M (Medium mode)
Approx. 105 C.F.M (Low mode)
30 Watt Incandescent light bulb

Section 1 Basic Information
1-9
3-Pronged Plug Grounded
Receptacle Box
Grounding Pin
3-Pronged Receptacle
Grounding Instructions
This oven is equipped with a three prong grounding
plug. It must be plugged into a wall receptacle that is
properly installed and grounded in accordance with the
National Electrical Code, local codes and ordinances.
In the event of an electrical short circuit, grounding
reduces the risk of electric shock by providing an escape
wire for the electric current.
Electrical Requirements
The oven is equipped with a 3-prong grounding plug.
DO NOT UNDER ANY CIRCUMSTANCES CUT OR
REMOVE THE GROUNDING PIN FROM THE PLUG.
The power supply cord and plug must be connected to a
separate 120 Volt AC, 60 Hz, 15 Amp. or more dedicated
line, using a grounded receptacle. When installing this
appliance, observe all applicable codes and ordinances.
A short power-supply cord is provided to reduce risks of
becoming entangled in or tripping over a longer cord.
Where a two-pronged wall-receptacle is encountered,
it is the personal responsibility and obligation of the
customer to contact a qualified electrician and have it
replaced with a properly grounded three-pronged wall
receptacle or have a grounding adapter properly
grounded and polarized.
If an extension cord must be used, it should be a 3-wire,
15 amp. or more cord. Do not drape over a countertop
or table where it can be pulled on by children or tripped
over accidentally.
Improper use of the grounding plug can result in
a risk of electric shock.
WARNING

4. Vent Top
5. Glass Turntable:
6. Cooktop light
*UHDVHoOWHUV
8. Control Panel: Touch the pads on this panel to
perform all functions.
The turntable reverses rotation each time the
microwave oven door is opened and closed.
This helps cook food evenly. Do not operate the
microwave oven without the turntable in place.
To Install:
 Place the support on the oven cavity bottom.
2. Place the turntable on the support. Fit the raised,
curved lines in the center of the turntable bottom
between the three spokes of the hub. The rollers on
WKHVXSSRUWVKRXOGoWinside the turntable bottom
ridge.
See "Caring for the Filters" section.
glass
Section 1 Basic Information
1-10
Oven Diagram
Located on back of Control Panel.
The microwave oven is designed to make
your cooking experience as enjoyable and
productive as possible. To get you up and
running quickly, the following is a list of the
oven's basic features:
1. Metal Shielded Window:
prevents microwaves from escaping.
It is designed as a screen to allow you
to view food as it cooks.
2. Model and Serial Number Plate
3. Cooking Guide label
A. Glass Turntable
C. Hub
B. Support
A
B
C
The shield
9. Wiring Diagram-
Note: Do not remove the mylar film from inside of door
4
9
10
12 35
66
778

Sect ion 2 Operat ion
2-1
The following is a description of component functions
during oven operation.
OFF CONDI TI ON
Closing the door activates the door sensing switch and
secondary interlock switch. (In this condition, the
monitor switch contacts are opened.) When oven is
plugged in, 120 volts AC is supplied to the control unit.
1. The display will show “PLEASE SET TIME OF DAY
To set any program or set the clock, you
must first touch the STOP/CLEAR button. The dis-
play will clear, and “ : “ appears.
COOKI NG CONDI TI ON
Program desired cooking time touching the NUMBER
pads. When the START pad is touched, the following
operations occur:
1. The contacts of relays are closed and components
connected to the relays are turned on as follows.
2. 120 volts AC is supplied to the primary winding of
the power transformer and is converted to about
3.3 volts AC output on the filament winding, and
approximately 2000 volts AC on the high voltage
winding.
3. The filament winding voltage heats the magnetron
filament and the H.V. winding voltage is sent to a
voltage doubler circuit.
4. The microwave energy produced by the magnetron
is channeled through the waveguide into the cavity
feedbox, and then into the cavity where the food
is placed to be cooked.
5. Upon completion of the cooking time, the power
transformer, oven lamp, etc. are turned off, and the
generation of microwave energy is stopped. The
oven will revert to the OFF condition.
6. When the door is opened during a cook cycle,
monitor switch, door sensing switch, primary
interlock switch, and secondary interlock relay are
activated with the following results. The circuits to
the stirrer motor, the cooling fan motor, the turn-
table motor, and the high voltage components are
de-energized, and the digital read-out displays the
time still remaining in the cook cycle when the door
was opened.
7. The monitor switch, which is electrically monitoring
the operation of the primary interlock switch and
door sensing switch, is mechanically associated
with the door so that it will function in the following
sequence.
(1) When the door opens from a closed position,
the secondary interlock relay, door sensing
switch and primary interlock switch open their
contacts, and then the monitor switch contacts
close.
(2) When the door is closed from the open position,
the monitor switch contacts open first. Then the
contacts of the primary interlock switch and
door sensing switch close, and contacts of the
relay (RY1) open.
If the primary interlock switch and secondary interlock
relay (RY2) fail with the contacts closed when the door
is opened, the closing of the monitor switch contacts will
form a short circuit through the monitor fuse, primary
interlock switch, relay (RY1) and secondary interlock
relay (RY2), causing the monitor fuse to blow.
Operat ing Sequence Descript ion
RELAY CONNECTED COMPONENTS
RY1
Oven Lamp
Fan motor / Stirrer motor
RY2 Power Transformer
RY8 Turntable Motor
RY
E - 04
E - 11
Humidity malfuction
Key short 1 minute
1
FAULT CODES

Section 2 Operation
2-2
POWER LEVEL P-0 TO P-90 COOKING
When Variable Cooking Power is programmed, the
120 volts A.C. is supplied to the power transformer
intermittently through the contacts of relay (RY2) which
is operated by the control unit within an interval second
time base. Microwave power operation is as follows:
The ON/OFF time ratio does not correspond with
the percentage of microwave power, because
approximately 2 seconds are needed for heating of
the magnetron filament.
NOTE
VENTILATION METHODS HOT AIR EXHAUST
1. Vertical Venting
For this venting method, hot air rising from the
conventional range below is drawn in by the hood fan
motor through the grease flters at the right and left
sides of the base cover, up through the right and left
sides of the oven cavity, then discharged vertically at rear
center top of the oven, into the customer’s vent system.
2. Horizontal Venting
The air handing is the same as Vertical Venting except
that fnal air discharge is directed horizontally out from
the top rear of oven into the customer’s vent system.
3. Re-circulation (Inside venting)
The air handing is the same as VERTICAL VENTING
except that the final air discharge is directed horizontally
through the upper front of the oven into the kitchen. In
this case, the accessory charcoal Filter RK-240 must be
provided to filter the air before it leaves the oven.
Vari-Mode ON TIME OFF TIME
Power 10 (High) (100% Power) 29 sec. 0 sec.
Power 9 (P-90) (Approx. 90%) 26 sec. 3 sec.
Power 8 (P-80) (Approx. 80%) 24 sec. 5 sec.
Power 7 (P-70) (Approx. 70%) 21 sec. 8 sec.
Power 6 (P-60) (Approx. 60%) 18 sec. 11 sec.
Power 5 (P-50) (Approx. 50%) 16 sec. 13 sec.
Power 4 (P-40) (Approx. 40%) 13 sec. 16 sec.
Power 3 (P-30) (Approx. 30%) 10 sec. 19 sec
Power 2 (P-20) (Approx. 20%) 7 sec. 22 sec.
Power 1 (P-10) (Approx. 10%) 5 sec. 24 sec.

Section 2 Operation
2-3
For HMV505U:

Section 2 Operation
2-4
For HMV505C:

Section 2 Operation
2-4
Touch Control Panel Assembly Outline
The touch control section consists of the following units.
(1) Key unit
(2) Control Unit: The Control unit consists of Logic Unit and
Power Unit.
The principal functions of these units and the signals
communicated among them are explained below.
KEY UNIT
CONTROL UNIT
Control unit consists of Logic Unit, power source circuit,
synchronizing signal circuit, reset circuit, buzzer circuit,
relay circuit indicator circuit and back light circuit.
1. (Logic Unit)
This Logic controls the key strobe signal, relay driving
signal for oven function and indicator signal.
2. Power Source Circuit
This circuit generates voltages necessary for the
control unit from the AC line voltage. In addition,
the synchronizing signal is available in order to
compose a basic standard time in the clock circuit.
Symbol Voltage Application
VC -5.3V Logic Unit(IC1)
3. Synchronizing Signal Circuit
The power source synchronizing signal is available in
order to compose a basic standard time in the clock
circuit. It incorporates a very small error because it
works on commercial frequency.
4. Reset Circuit
This circuit generates a signal which resets the Logic
5. Buzzer Circuit
The buzzer is responds to signals from the Logic unit to
emit audible sounds (key touch sound and
completion sound).
6. Door Sensing Switch
A switch to inform the Logic Unit if the door is open or
closed.
7. Relay Circuit
To drive the magnetron, fan motor, turntable motor,
hood motor, and light the oven lamp and hood lamp.
8. Indicator Circuit
This circuit consists of 25 segments and 4 common
electrodes using a Light Crystal Display.
9. Back Light Circuit
A circuit to drive the back light (Light emitting diodes
LD1-LD4).
DOOR OPEN MECHANISM
The door is opened by pulling the door handle, refer to
the Figure 2-3.
DOOR SENSING SWITCH AND PRIMARY
INTERLOCK SWITCH
The primary interlock switch is mounted in the upper
position of the latch hook. The door sensing switch in
the primary interlock system is mounted in the lower
position of the latch hook which is mounted on the upper
position of the latch hook. They are activated by the
latch heads on the door. When the door is opened, the
switches interrupt the circuit to all components. A cook
cycle cannot take place until the door is firmly closed,
thereby activating both interlock switches. The primary
interlock system consists of the door sensing switch and
secondary interlock relay located on the control circuit
board.
Figure 2-3. Door Open Mechanism
Component Descriptions
Latch Heads
Door
Latch Hook
Primary Interlock Switch
Monitor Switch
Door Sensing Switch
Remark: Logic Unit stands for Large Scale Integrated Circuit.
Unit (IC1) to the initial state when power is supplied.
The key unit is composed of a matrix, signals generated
in the Logic Unit are sent to the key unit through P20,
completed through the key unit and passed back to the
Logic unit through P43, P44, P45 and P46 to perform the
function that was requested.
P25, and P26. When a key pad is touched, a signal is
P21
P2
,

Section 2 Operation
2-5
MONITOR SWITCH
The monitor switch is activated (the contacts opened)
by the latch head on the door while the door is closed.
The switch is intended to render the oven inoperative, by
means of blowing the monitor fuse, when the contacts of
the secondary interlock relay (RY2) and primary interlock
switch fail to open when the door is opened.
Functions:
1. When the door is opened, the monitor switch
contact close (to the ON condition) due to their
being normally closed. At this time the secondary
interlock relay (RY2), and primary interlock switch
are in the OFF condition (contacts open) due to their
being normally open contact switches. The contacts
of relay (RY1) are in the ON condition (contacts
close).
2. As the door goes to a closed position, the monitor
switch contacts are first opened and then the door
sensing switch and the primary interlock switch
contacts close. (On opening the door, each of these
switches operate inversely.)
3. If the door is opened, and the secondary interlock
relay (RY2) and primary interlock switch contacts fail
to open, the monitor fuse blows simultaneously with
closing of the monitor switch contacts.
THERMAL CUT-OUT (CAVITY)
This thermal cut-out is located on the top of the oven
cavity. It is designed to prevent damage to the oven unit
if the food in the oven catches fre due to overheating
produced by improper setting of cooking time or failure
of control unit. Under normal operation, the thermal
cut-out remains closed. However, the thermal cut-out
will open at 248°F (120°C) causing the oven to shut
down.
Before replacing a blown monitor fuse test the
door sensing switch, secondary interlock relay
(RY2), relay (RY1), primary interlock switch and
monitor switch for proper operation. (Refer to
“Test Procedure”).
CAUTION
Monitor fuse and switch are replaced as an assembly.
NOTE
THERMAL CUT-OUT (HOOD)
This thermal cut-out located on the right base plate. It
is designed to automatically turn on the hood fan motor
whenever the hot air rising from the conventional range
below causes the temperature at the thermal cut-out to
rise to 158°F (70°C) or higher, thus removing this hot air
from around microwave oven. When the temperature
around the thermal cut-out drops to 104°F (40°C) or
lower, the thermal cut-out shuts off the hood fan motor.
TURNTABLE MOTOR
The turntable motor rotates the turntable located on
the bottom of the oven cavity, so that the foods on the
turntable cook evenly during cooking. Turntable will turn
in either direction.
COOLING FAN MOTOR
The cooling fan motor drives a blade which draws
external cool air. This cool air is directed through the
air vanes surrounding the magnetron and cools the
magnetron. This air is channelled through the oven
cavity to remove steam and vapors given off from the
heating foods. It is then exhausted through exhausting
air vents at the oven cavity.
HOOD FAN MOTOR
The hood fan motor is a four-speeds, single-phase,
double pole induction type, requiring a hood fan
capacitor. It is located outside the upper rear part of
the oven cavity. The hood fan motor removes hot air
from around the oven as it rises from the conventional
electric or gas range over which it is installed. This air is
then expelled either vertically or horizontally through the
customer supplied duct system, or discharged back into
the kitchen.
HOOD LAMP
The hood lamps are mounted at the hood lamp angle on
the base cover. The hood lamps can be turned off and
on.

Section 3 Troubleshooting and Testing
3-1
Troubleshooting Guide
When troubleshooting the microwave oven, it is helpful to follow the Sequence of Operation in performing the
checks. Many of the possible causes of trouble will require that a specific test be performed. These tests are
given a procedure letter which will be found in the “Test Procedure “section.
If the oven becomes inoperative because of a blown monitor fuse, check the monitor switch, relay
(RY1) secondary interlock relay (RY2), door sensing switch and primary interlock switch before
replacing the monitor fuse. If the monitor fuse is replaced, the monitor switch must also be replaced.
CAUTION
Whenever troubleshooting is performed with the power supply cord disconnected. It may in, some
cases, be necessary to connect the power supply cord after the outer case has been removed, in this
event:
1. Disconnect the power supply cord, and then remove outer case.
2. Open the door and block it open.
3. To discharge high voltage capacitor, wait for 60 seconds and then short-circuit the connection of
the high-voltage capacitor (that is the connecting lead of the high-voltage rectifier) against the
chassis with the use of an insulated screwdriver.
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.
WARNING
When the testing is completed:
1. Disconnect the power supply cord.
2. Open the door and block it open.
3. To discharge high voltage capacitor, wait for 60 seconds and then short-circuit the connection of
the high-voltage capacitor (that is the connecting lead of the high-voltage rectifier) against the
chassis with the use of an insulated screwdriver.
4. Reconnect the leads to the primary of the power transformer.
5. Reinstall the outer case (cabinet).
6. Reconnect the power supply cord after the outer case is installed.
7. Run the oven and check all functions.
WARNING
Microwave ovens do not run with the microwave empty. To test for the presence of microwave energy within a cavity,
of cold water on the oven turntable, close the door and set the power to HIGH and then set the microwave
two (2) minutes. When the two minutes has elapsed (timer at zero) carefully check that the water is now hot.
water remains cold carry out Before Servicing procedure and re-examine the connections to the component being
tested.
When all service work is completed and the oven is fully assembled, the microwave power output should be checked
and a microwave leakage test should be carried out.
place a cup
timer for
If the

Section 3 Troubleshooting and Testing
3-2
HUMIDITY SENSOR
8
6/7
10

Section 3 Troubleshooting and Testing
3-3
Procedure
Letter
A
Component Test
MAGNETRON ASSEMBLY TEST
1. Disconnect the power supply cord, and then remove outer case.
2. Open the door and block it open.
3. Discharge high voltage capacitor. (See Warnings and Instructions on page 3-1)
4. To test for an open filament, isolate the magnetron from the high voltage circuit. A continuity
check across the magnetron filament leads should indicate less than 1 ohm.
5. To test for a shorted magnetron, connect the ohmmeter leads between the magnetron filament
leads and chassis ground. This test should indicate an infinite resistance. If there is little or no
resistance the magnetron is grounded and must be replaced.
6. Reconnect all leads removed from components during testing.
7. Reinstall the outer case (cabinet).
8. Reconnect the power supply cord after the outer case is installed.
9. Run the oven and check all functions.
MICROWAVE OUTPUT POWER
Power output of the magnetron can be measured by performing a water temperature rise test. This
test should only be used if above tests do not indicate a faulty magnetron and there is no defect in
the following components or wiring: silicon rectifier, high voltage capacitor and power transformer.
This test will require a 16 ounce (453 cc.) measuring cup and an accurate mercury thermometer or
thermocouple type temperature tester. For accurate results, the following procedure must be
followed carefully:
1. Fill the measuring cup with 16 oz. (453 cc.) of tap water and measure the temperature of
the water with a thermometer or thermocouple temperature tester. Stir the thermometer or
thermocouple through the water until the temperature stabilizes. Record the temperature of the
water.
2. Place the cup of water in the oven. Operate oven at 100% POWER 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 until the maximum temperature is recorded.
4. Subtract the cold water temperature from the hot water temperature. The normal result should
be 29.2 to 54.2°F (16.2 to 30.1°C) rise in temperature. If the water temperatures are accurately
measured and tested for the required time period the test results will indicate if the magnetron
tube has low power output (low rise in water temperature) which would extend cooking time or
high power output (high rise in water temperature) which would reduce cooking time. Because
cooking time can be adjusted to compensate for power output, the magnetron tube assembly
should be replaced only if the water temperature rise test indicates a power output well beyond
the normal limits. The test is only accurate if the power supply line voltage is 120 volts and the
oven cavity is clean.
Test Procedures
High voltages are present during the cook cycle, so extreme caution should be
observed. Discharge the high voltage capacitor before touching any oven components
or wiring.
WARNING