Garland EM-C180 User Manual
SERVICE MANUAL SUPPLEMENT
CAUTION
WARNING TO SERVICE
TECHNICIANS
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.
(c) 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.
(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)(i) A microwave leakage check to verify compliance with the Federal performance standard should be
performed on each oven prior to release to the owner. (For U.S.A)
(e)(ii) A microwave leakage check to verify compliance with the Canadian Regulation, HEALTH AND WELFARE,
SOR/79-920 should be performed on each oven prior to release to the owner. (For CANADA)
See the Service Manual of EM-C180US(SM-640179)
except the items described in this Service Manual.
PRODUCT CODE NO. 437-453-00
for Model EM-C180
Microwave Oven
FORM # EM-C180 (02/05)
CAUTION
For microwave energy emission
On every service call. A check for micro-
wave energy emission must be made
according to the following manner.
Measurement of energy emission
In the area emitting the highest reading, switch the
meter to SLOW RESPONSE and take a reading for
minimum of three (3) seconds. We recommended the
pattern outline shown below when the door surface is
surveyed.
NOTE: Periodically check to be sure that the probe tip
is not worn or dirty.
Measurement must be made with the microwave oven
operating at its maximum output and containing a load
of 275±15 milliliters of tap water initially at 20°±5°
celsius (68±9°F) placed within the cavity at the center.
NOTE:The water container m ust be a 600 milliliter bea-
ker and made of an electrically none conductive material such as glass or plastic.
The cook tray must be in place when measuring
emission.
A properly operating door and seal assembly will normally register emission no greater than 4 mW/cm2 to
allow for measurement uncertainty with the cooking
shelf or tray in place.
All repairs must be performed in such a
manner that microwave energy emission
is minimal.
Follow the instructions supplied with the detector being used and perform an R.F. emission test around the
door front, and all edges and vent of the outer case.
The cabinet (wrapper) must be in place and the oven
fully assembled.
When performing an emission survey, with the meter
on FAST RESPONSE, the movement of the detector
probe shall not exceed one (1) inch per second.
The following U.S. standard applies to microwave ovens:
21 CFR 1030.10, Perf ormance Standard f or Microw a v e
Ovens.
It requires that the power density of the microwave
radiation emitted by a microwave oven shall not exceed five (5) milliwatts per square centimeter at any
point 5 centimeters (about 2 inches) or more from the
external surface of the oven.
All microwave ovens exceeding the emission level of 4
mW/cm2 must be reported to Dept. of Service for microwave ovens and the manufacturer immediately.
The owner should be told not to use the microwave
oven until it has been repaired completely.
If a microwave oven is found to operate with the door
open, report to Dept. of Service, the manufacturer and
CDRH* immediately. Also tell the owner not to use the
oven.
*CDRH: Center for Device and Radiological Health.
The interlock monitor switch acts as the final safety
switch protecting the customer from microwave radiation. If the interlock monitor switch operates properly
and the door interlock switch fails, the fuse will blow.
If this happens, all interlock switches must be replaced.
The contacts of the interlock switches may be welded
together.
- TABLE OF CONTENTS -
Adjustment Procedures.............................................1
Specifications............................................................ 2
Power output Measurement ......................................2
Precautions and Repair Service Tips .......................2
Circuit Diagram .........................................................3
1. ADJUSTMENT PROCEDURES
TO AVOID POSSIBLE EXPOSURE TO MICROWAVE
ENERGY LEAKAGE, THE FOLLOWING ADJUSTMENTS OF THE INTERLOCK SWITCHES SHOULD
BE MADE ONLY BY AUTHORIZED SERVICE PERSONNEL.
The service center should have the designated
detector to measure the microwave energy
leakage after the repair or adjustment.
NOTE: Detector to be used at the service center is
NARDA 8100, 8200 or the equivalent.
INTERLOCK SWITCH, INTERLOCK MONITOR
SWITCH AND DOOR SENSING SWITCH ADJUSTMENT
(Figure 1)
(1) Loosen 2 screws securing the lever stopper.
(2) Adjust the lever stopper position so that it is pushed
up and pulled backwards until there is zero gap
between the latch lever and the switch body on the
interlock switch. At the same time there is zero gap
between the latch lever and the switch body on the
door sensing switch when the door latch is securely
locked.
(3) Tighten the lever stopper screws securely.
(4) Make sure the interlock monitor switch closes
after the interlock switch opens when the door is
opened very slowly, according to “CHECKOUT
PROCEDURE FOR SWITCHES” on page 6.
(5) Make sure the interlock monitor switch opens
before the interlock switch closes when the door is
closed very slowly, according to CHECKOUT PRO-
CEDURE FOR SWITCHES” on page 6.
(6)(i) Make sure the microwave energy leakage should
be no greater than 4 mW/cm2 to allow to measure-
ment uncertainty when measured with a detector.
(All service adjustments must be made for mini-
mum microwa ve energy leakage readings .) (For US)
(6)(ii) Make sure the microwave energy leakage is
below the limit of 1 mW/cm2 (at 275cc water load),
5 mW/cm2 (at no load) and 5 mW/cm2 (at 275 cc
water load without cabinet) when measured with a
detector.
Test Procedures and Troubleshooting...............4•`10
Disassembly Instructions .............................. 11•`14
Exploded View and Pa rts List ........................ 15•`22
Overall Circuit Diagram.................................23•`25
(All service adjustments must be made for minimum
microwav e energy leakage readings .) (F or Canada)
NOTE: If the interlock monitor circuit operates and at
the same time the fuse blows with the door
open, be sure to replace the relay circuit board
, Interlock switch and monitor switch.
Lever stopper
Interlock monitor
switch
Latch Lever
Interlock
switch (Secondary
interlock switch)
Latch Lever
Door sensing
switch
(Primary interlock
switch)
Screws
Figure 1
- 3 -
2.SPECIFICATIONS
Microwave output ................1,800W to 180W
Frequency ...........................2,450MHz
Power supply.......................208V, 60Hz
Rated current ......................13 Amp.
Safety Device......................
Thermal protector(Magnetron) 150°C(270°F)Open
(Thermostat) 80°C(144°F)Close
Thermistor (Magnetron) 200°C(360°F) Open
108°C(194°F)Close
Thermistor(Duct)................120°C(216°F) Open
Fuse (Cartr idge Type) .................250V 10A
Micro switch, Relay
Interlock Switch
Interlock monitor Switch
Door sensing Switch and
Relay RL-3 and 4
Max. input time....................Electronic Digital, up to
Manual
Overall Dimensions........422(W)x540(D)x335(H) mm
Oven cavity size ............330(W)x330(D)x230(H) mm
Effective Capacity of Oven Cavity.........19.1liters
Net weight ...........................32Kg
3. POWER OUTPUT MEASUREMENT
NOTE: The power output specification, 1800W on this
model is measured with IEC measurement. The power
output is measured with two(2) liters water is equivalent to 1800W in measurement with IEC, when measured with the following power output.
(1)1. Fill two beakers, one liter of tap water respec tively
2. Use an accurate thermometer and measure each
water temperature respectively.
(2) Place beakers side by side in center of the
ceramic tray.
(3) Close the door,set the “TIME” for two minutes.
Touch the “START” key and heat the water for
exactly two minutes.
(4)Take the beakers out, immediately stir the water
and measure the water temperatures respectively.
(5) Calculate the temperature rise of water in each
beaker . Then calculate the average value of the two
temperature rises.( Ģt)
(6) The teperature rise shall be in the following range;
Average Temp. Rise
Minimum 23.1°C
Maximum 28.3°C
Po w er output is affected by the line voltage under load.
(7) For correct Power output measurement, the line
voltage under load must be 208±2Volts.
4.PRECATIONS AND REPAIR SERVICE TIPS
PRELIMINARY
10min./Memory 30min.
A. SINCE NEARLY 4,000 V OLTS EXISTS IN SOME
CIRCUITS OF THIS MICROWAVE OVEN, REPAIRS SHOULD BE CARRIED OUT WITH
GREAT CARE.
B. TO AVOID POSSIBLE EXPOSURE TO MICRO-
WAVE ENERGY LEAKAGE, THE FOLLOWING
PRECA TIONS MUST BE TAKEN BEFORE SERVICING.
(1) Before the power is applied.
(a) Open and close door several times to make
sure the interlock switch, door sensing switch
and interlock monitor switch operate properly.
(Listen for the clicking sound from switches.)
Make sure the interlock monitor switch is
closed after the interlock switch and door sens-
ing are open when the door is opened.
(See pages 1 and 6)
(b) Make sure the perf orated screen and the choke
dielectric of the door are correctly mounted.
(2) After the power is applied.
(a) Open and close the door to see if the interlock
mechanism operates properly.
(b) Check microwave energy leakage with a leak-
age detector and confirm the energy leakage
is below 5mW/cm
2
(3) Do not operate the unit until it is completely
repaired of any of the following conditions.
(a) Door is not closed firmly against the cavity
front.
(b) The hinge is broken.
(c) The choke dielectric or the door seal is dam-
aged.
(d) The door is bent or warped, or there is any
other visible damage to the oven that may
cause microwave energy leakage.
Note: Always keep the seal clean.
(e) Make sure that there are no defective parts in
the interlock mechanism.
(f) Make sure that there are no defective par ts in
the microwave generating and transmission
assembly. (especially wave guide).
(4) The following items should be checked after
the unit is repaired.
(a) The interlock monitor switch is connected cor-
rectly and firmly.
(b) The magnetron gasket on the magnetron is
properly positioned.
(c) Waveguide and oven cavity are intact. (No
leakage of microwave energy).
(d) The door can be properly closed and the safety
switches work properly.
(e) The oven must be stopped when the door is
opened or the time is up.
The ov en must not be operated with any of the abo v e
components removed or bypassed.
- 2 -
6. TEST PROCEDURES AND TROUBLESHOO TING
CAUTION
-DISCONNECT THE POWER SUPPLY CORD FROM THE WALL
OUTLET WHENEVER REMO VING THE CABINET FROM THE UNIT.
PROCEED WITH TESTS ONLY AFTER DISCHARGING THE HIGH
VOLTAGE CAPACITORS AND REMOVING THE LEAD WIRES ON
THE PRIMARY WINDING OF THE HIGH VOLTAGE TRANSFORMERS FOR LOWER AND UPPER MA GNETRONS.
(SEE FIGURE 3)
A. TEST PROCEDURES
COMPONENT
MAGNETRON
CHECKOUT PROCEDURE RESULT
1) Check for resistance: Across the filament terminal of the magnetron with an ohm - meter
on Rx1 scale.
Figure 4
2) Check for resistance: Between each filament
terminal of the magnetron and the chassis
ground with an ohm-meter on highest scale.
PRIMARY
WINDINGS
Secondary
Windings
Filament
Windings
Figure 3
Normal reading:
Less than 1 ohm.
Normal reading:
Infinite ohms.
HIGH-VOLTAGE
TRANSFORMER
1) Measure the resistance:
With an ohm-meter on R x1 scale.
a. Primary winding;
b. Filament winding;
c. Secondary winding;
2) Measure the resistance:
with an ohm-meter on highest scale.
a. Primary winding to ground;
b. Filament winding to ground;
Figure 5
Figure 6
Normal reading:
Approximately 1.0 ohms
Less than 1 ohm.
Approximately 60 ohms
Normal reading:
Infinite ohms.
Infinite ohms.
Note: Remove varnish of measured point.
- 6 -
COMPONENT
HIGH-VOLTAGE
CAP A CITOR
Including internal
bleeder
resistor
CHECKOUT PROCEDURE RESULT
Measure the resistance: Across two terminals with
an ohm-meter on highest scale.
Figure 7
Normal reading:
Momentarily indicates several ohms, and
gradually to 10 meg-ohms.
Abnormal reading:
Indicates continuity or 10 meg-ohms
from the beginning.
HIGH-VOLTAGE
DIODE
Measure the resistance: Across two terminals with
an ohm-meter on highest scale.
Figure 8
Normal reading:
Indicate about middle position in one
direction (forward) and infinite ohms in
the reverse direction, using ohm meter
with a 9V battery.
NOTE
- Some digital meter may show more
than 0 ohms or infinite ohms even in a
forward direction because the low measuring voltage of the meter does not
allow the meter to pass through the high
voltage diode. Use an ohm meter with
a 9V battery.
Abnormal reading:
Indicates continuity or infinite ohms in
both directions.
- 7 -
COMPONENT
TOUCH KEY
BOARD
CHECKOUT PROCEDURE RESUL T
Measure the resistance between terminals of
FPC connector after removing it from
S101.(Figure 10)
NOTE
- When reconnecting the FPC connector, make
sure the holes on the connector are properly
inserted in hook of the plastic fastener in S101.
MATRIX CIRCUIT FOR
TOUCH KEY BOARD
FPC CONNECTOR
When When not
Resistance touched touched
Value Less than More than
1 K ohms 1 meg ohms
When checking the POWER key ,
connect the ohm-meter as illustrated
below.
TERMINAL OF FPC CONNECTOR
FIGURE 10
CHECKOUT PROCEDURE FOR SWITCHES
Disconnect the lead wires from the switches and check for the continuity of the switches, connecting an ohm-meter
to its terminals.
SWITCHES
(SEE Figure 1 on page 1)
INTERLOCK SWITCH
DOOR SENSING SWITCH
INTERLOCK MONITOR
SWITCH
CHECKOUT PROCEDURES DOOR OPEN DOOR CLOSED
Terminals "COM" and "NO"
Ter minals "COM" and "NC"
CAUTION: After checking the switches, make sure that the interlock monitor switch is properly connected according
to the CIRCUIT DIAGRAM on page 3.
- 8 -
WARNING:
When removing the cabinet, you m ust disconnect
the power supply cord from the wall oulet f or your
safety. Only the chec kout procedure below needs
the power supply on. TAKE GREAT CARE to avoid
possible electrical shock.
For your safety, proceed with the test only
after removing the wire leads from the primary winding of the high voltage transformer
Primary
Winding
Primary
Winding
Lower
Upper
COMPONENT
POWER
P.C.B
CHECKOUT PROCEDURE RESULT
Check voltage at S104 and S105 after removing each connector (female) from power circuit
board.
Pin No.3 (Ground) and 4,5, 1,2 at S105.
Pin No.1 and 2 at S104.
CAUTION:
For your safety, proceed with the test only
after removing the wire leads from the pri-
mary winding of high voltage transformer.
Test procedures:
a) Make sure that the power supply cord is not
plugged in.
b) Remove the connector S104 and S105 from
the power circuit board.
c) Plug the power supply cord : back in.
d) And then, measure each voltage.
Normal reading:
Connection
Pin No., Voltage(V)
S105
#3 to #4 DC 12
#3 to #5 DC 16
#3 to #1 DC 30
#3 to #2 DC 35
S104
#1 to #2 AC 2.4
CONTROL
P.C.B
Measure the voltage: Between test points TP-1,
TP-2 ,TP-3 and ground (See figure 16 on page
23)
Note
- Proceed with the check of the control P.C.B to
see if any one of the measured values is different from the specified values.
- 9 -
Test point
TP, Voltage(V)
TP-1 DC - 5
TP-2 DC - 12
TP-3 DC - 16
TP-4 DC - 35
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