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Model
R-216 (serv.man2)
Pages
32
Size
1.05 MB
Type
PDF
Document
Service Manual
Brand
Device
Home Appliance / Microwave Oven / Complete
File
r-216-sm2.pdf
Date

Sharp R-216 (serv.man2) Service Manual ▷ View online

R-216(W)
5
FUNCTION OF IMPORTANT COMPONENTS
THERMAL CUT-OUT 125˚C (OVEN)
The thermal cut-out located on the top of the oven cavity
is designed to prevent damage to the oven if the foods in
the oven catch fire due to over heating produced by
improper setting of cook time or failure of control unit.
Under normal operation, the thermal cut-out remains
closed. However, when abnormally high temperatures are
reached within the oven cavity, the thermal cut-out will
open at 125˚C, causing the oven to shut down. The
defective thermal cut-out must be replaced with a new
one.
THERMAL CUT-OUT 95˚C (MAGNETRON )
The thermal cut-out located on the top of the oven cavity
is designed to prevent damage to the magnetron if an over
heated condition develops in the tube due to cooling fan
failure, obstructed air guide, dirty or blocked air intake, etc.
Under normal operation, the thermal cut-out remains
closed. However, when abnormally high temperatures are
reached within the magnetron, the thermal cut-out will
open at  95˚C, causing the oven to shut down. When the
magnetron has cooled  to 75˚C, the thermal cut-out closes
and cook cycle will resume.
TURNTABLE MOTOR
The turntable motor drives the roller stay to rotate the
turntable.
FAN MOTOR
The 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 chan-
nelled through the oven cavity to remove steam and
vapours given off from the heating foods. It is then ex-
hausted through the exhausting air vents at the oven
cavity.
NOISE FILTER
The noise filter prevents the radio frequency interference
that might flow back in the power circuit.
DOOR OPEN MECHANISM
The door is opened by pulling the door, refer to the Figure
D-1.
Figure D-1. Door Open Mechanism
MONITORED LATCH SWITCH  AD 2ND. INTER-
LOCK RELAY CONTROL SWITCH
1. When the oven door is closed, the contacts (COM-NO)
must be closed.
2. When the oven door is opened, the contacts (COM-
NO) must be opened.
MONITOR SWITCH
1. When the oven door is closed, the contacts (COM-NC)
must be opened.
2. When the oven door is opened, the contacts (COM-
NC) must be closed.
3. If the oven door is opened and the contacts (COM-NO)
of the monitored latch switch fail to open, the fuse
T6.3A blows simultaneously with closing the contacts
(COM-NC) of the monitor switch .
CAUTION: BEFORE REPLACING A FUSE TEST THE
MONITORED LATCH SWITCH AND
MONITOR SWITCH   FOR PROPER OP-
ERATION. (REFER TO CHAPTER "TEST
PROCEDURE".)
FUSE T6.3A
1. The fuse T6.3A blows when the contacts (COM-NO) of
the monitored latch switch remain closed with the oven
door open and when the monitor switch   closes.
2. If the wire harness or electrical components are short-
circuited, the fuse T6.3A blows to prevent an electric
shock of fire hazard.
HIGH VOLTAGE FUSE
The high voltage fuse blows when the high voltage rectifier
or the magnetron is shorted.
Latch Heads
Latch Hook
Door
Monitor
Switch
Monitored
Latch
Switch
2nd. Interlock
Relay Control
 Switch
6
R-216(W)
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.
IMPORTANT: If the oven becomes inoperative because
of a blown fuse T6.3A in the monitored
latch switch  - monitor switch  circuit, check
the monitored latch switch and monitor
switch  before replacing the fuse T6.3A.
TROUBLESHOOTING GUIDE
MAGNETRON
HIGH VOLTAGE TRANSFORMER
H.V. RECTIFIER ASSEMBLY
HIGH VOLTAGE WIRE
HIGH VOLTAGE CAPACITOR
MONITORED  LATCH SWITCH
2ND. INTERLOCK RELAY CONTROL SWITCH
MONITOR SWITCH
THERMAL CUT-OUT 125˚C (OVEN)
THERMAL CUT-OUT 95˚C (MG)
FAN MOTOR
TURNTABLE MOTOR
FUSE T6.3A
CONTROL PANEL
TACT SWITCH
RELAY 
RY1,
RELAY 
RY2,
FOIL PATERN ON P.W.B.
POWER SUPPLY CORD
SHORTED WIRE HARNESS
OPENED WIRE HARNESS
OVEN LAMP
WALL OUTLET
MISADJUSTMENT SWITCH
HOME FUSE OR BREAKER
BLOCKED COOLING FAN
BLOCKED VENTILATION
NOISE FILTER
H.V. FUSE
Home fuse blows when power
supply cord is plugged into wall
outlet.
FUSE T6.3A blows when
power supply cord is plugged
into wall outlet.
Oven does not start when the
timer is set.
Oven lamp does not light (Other
function is normal.)
Fan motor does not operate.
(Other function is normal.)
Turntable motor does not op-
erate. (Other function is nor-
mal.)
Oven or any electrical parts
does not stop when cooking
time is 0.
Oven seems to be operating
but little or no heat is produced
in oven load. (Microwave
power level is set at HIGH)
Oven does not seems to be
operating properly when
MEDIUM HIGH, MEDIUM,
MEDIUM LOW or LOW is set.
(Oven operates properly at
HIGH.)
Oven goes into cook cycle but
shuts down before end of cook-
ing cycle.
Oven lamp, turntable motor
and fan motor do not operate.
The microwave power level can
not be changed.
OFF
CONDITION
PROBLEM
CONDITION
POSSIBLE CAUSE
AND
DEFECTIVE PARTS
TEST PROCEDURE
ON
CONDITION
CK = Check / RE = Replace
A B C
CK
D E E E F   F   G  G   H   K   L M M N
RECKCKRE CKCKCK CK CK
I J
R-216(W)
7
TEST PROCEDURES
PROCEDURE
LETTER
COMPONENT TEST
CARRY OUT 3D CHECK.
Isolate the magnetron from high voltage circuit by removing all leads connected to filament terminal.
To test for an open circuit filament use an ohmmeter to make a continuity test between the magnetron
filament terminals, the meter should show a reading of less than 1 ohm.
To test for short circuit filament to anode condition, connect ohmmeter between one of the filament
terminals and the case of the magnetron (ground). This test should be indicated an infinite resistance.
If a low or zero resistance reading is obtained then the magnetron should be replaced.
MICROWAVE OUTPUT POWER TEST
The power output of this oven is rated using the method specified by  IEC 60705. Full details of how
to curry out this procedure can be found in the Sharp Technical Training notes which is available from
Sharp Parts Centre (part number SERV-LITMW01).
The IEC60705 procedure must be carried out using laboratory-type procedures and equipment.
These requirements make the procedure unsuitable for routine performance checks.
NOTE: The following test method gives an indication of the output power only, it cannot be used to
establish the actual/rated output power. If the true output power is required, then the IEC60705
test method must be used.
Alternative simplified method:
1. Place 2  litres of cold water (between 12
°C and 20°C) in a suitable container.
2. Stir the water and measure the temperature in 
°C. Note temperature as T1.
3. Place the container in the microwave and heat the water for 1 minute and 48 seconds on full power.
NOTE: The operation time of microwave oven includes "3" sec. (3 sec. is magnetron filament
heat-up time.)
4. When the 1 minute and 48 seconds is completed, remove the  container and stir the water. Note
the water temperature as T2.
5. Calculate the output power using the following formula:
R.F. Power Output = (T2 - T1) x 80.
NOTE: The result from this test should be within the allowance of 2000cc alternative method.
(
±
10%).
MICROWAVE LEAKAGE TEST
This oven should be tested for microwave leakage on completion of any repair or adjustment, following
the procedure described in the Sharp Technical Training notes (part number SERV-LITMW01). The
maximum leakage permitted in BS EN 60335-2-25 is 50W/m
(equivalent to 5W/m
2
), however it is not
normal to detect any significant leakage, therefore, any leakage which is detected should be
investigated.
It is essential that only leakage detectors with current calibration traceable to National Physical
Laboratories are used.
Suitable leakage detectors: CELTEC A100
APOLLO X1
A
MAGNETRON TEST
NEVER TOUCH ANY PART IN THE CIRCUIT WITH YOUR HAND OR AN INSULATED TOOL
WHILE THE OVEN IS IN OPERATION.
B
HIGH VOLTAGE  TRANSFORMER TEST
WARNING:
High voltage and large currents are present at the secondary winding and
filament winding of the high voltage transformer. It is very dangerous to work
near this part when the oven is on. NEVER make any voltage measurements
of the high-voltage circuits, including the magnetron filament.
8
R-216(W)
F
THERMAL CUT-OUT TEST
E
SWITCH TEST
Table: Terminal Connection of Switch
Plunger Operation
COM to NO
COM to NC
Released
Open circuit
Short circuit
Depressed
Short circuit
Open circuit
COM; Common terminal,
NO;
Normally open terminal
NC;
Normally close terminal
If incorrect readings are obtained, make the necessary switch adjustment or replace the switch.
CARRY OUT 4R CHECKS.
CARRY OUT 3D CHECKS.
Isolate the switch to be tested and using an ohmmeter check between the terminals as described in
the following table.
TEST PROCEDURES
PROCEDURE
LETTER
COMPONENT TEST
CARRY OUT 3D CHECKS.
Disconnect the leads to the primary winding of the high voltage  transformer. Disconnect the filament
and secondary winding connections from the rest of the HV circuitry. Using an ohmmeter, set on a low
range,  it is possible to check the continuity of all three winding. The following readings should be
obtained:-
a. Primary winding .......................... 2.8 ohms approximately
b. Secondary winding .................... 189 ohms approximately
c. Filament winding .....................................  less than 1 ohm
If the readings obtained are not stated as above, then the high voltage transformer is probably faulty
and should be replaced.
CARRY OUT 4R CHECKS.
C
HIGH VOLTAGE RECTIFIER TEST
CARRY OUT 3D CHECKS.
Isolate the high voltage rectifier assembly from the HV circuit. The high voltage rectifier  can be tested
using an ohmmeter set to its highest range. Connect the ohmmeter across the terminal of the high
voltage rectifier and note the reading obtained. Reverse the meter leads and note this second reading.
The normal resistance is infinite in one direction and more than 100 k
Ω in the other direction.
CARRY OUT 4R CHECKS.
NOTE: FOR MEASUREMENT OF THE RESISTANCE OF THE RECTIFIER, THE BATTERIES OF
THE MEASURING INSTRUMENT MUST HAVE A VOLTAGE AT LEAST 6 VOLTS, BECAUSE
OTHERWISE AN INFINITE RESISTANCE MIGHT BE SHOWN IN BOTH DIRECTIONS.
CARRY OUT 3D CHECKS.
A. Isolate the high voltage capacitor from the circuit.
B. Continuity check must be carried out with measuring instrument which is set to the highest
resistance range.
C. A normal capacitor shows continuity for a short time (kick) and then a resistance of about 10M
Ω after
it has been charged.
D. A short-circuited capacitor shows continuity all the time.
E. An open capacitor constantly shows a resistance about 10 M
Ω because of its internal 10MΩ
resistance.
F. When the internal wire is opened in the high voltage capacitor, the capacitor shows an infinite
resistance.
G. The resistance across all the terminals and the chassis must be infinite when the capacitor is  normal.
If incorrect reading are obtained, the high voltage capacitor must be replaced.
CARRY OUT 4R CHECKS.
D
HIGH VOLTAGE CAPACITOR TEST
CARRY OUT 3D CHECKS.
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