DOWNLOAD Sharp R-895M (serv.man6) Service Manual ↓ Size: 483 KB | Pages: 7 in PDF or view online for FREE

Model
R-895M (serv.man6)
Pages
7
Size
483 KB
Type
PDF
Document
Service Manual
Brand
Device
Home Appliance / Microwave Oven / Troubleshooting guide and test procedures
File
r-895m-sm6.pdf
Date

Sharp R-895M (serv.man6) Service Manual ▷ View online

R-895M - 12
Fuse F8A blows when the door is opened.
Home fuse blows when power cord is plugged into wall outlet.
Fuse 15A blows when power cord is plugged into wall outlet.
Nothing appears in display when power cord is plugged into wall outlet 
and the door is opened and closed.
Display does not operate properly when STOP/CLEAR key is touched.
Oven lamp does not light when door is opened. (Display operates.)
Oven does not start when the START key is touched. (Display operates.)
Oven lamp does not light  and turntable motor does not operate.
Fan motor does not operate. (Oven lamp lights.)
Convection fan motor does not operate. (Oven lamp lights.)
Turntable motor does not operate. (Oven lamp lights.)
Oven or any electrical parts (except fan motor) does not stop when 
cooking time is 0 or STOP/CLEAR key is touched.
Oven stops after 4 minutes and 15 seconds since START key is 
touched. (Except Microwave mode)
Display operates properly but all electrical parts do not operate.
Oven goes into cook cycle but shuts down before end of cooking cycle.
After cooking, the temperature of oven cavity is higher than 105
˚C but 
fan motor does not operate.
Oven seems to be operating but little or no heat is produced in oven 
load. (Microwave power control is set at HIGH)
Oven does not seem to be operating properly during variable cooking 
condition except HIGH cooking condition.
Oven goes into cook cycle but shuts down before end of cooking cycle.
Convection cooking mode does not heat.
Oven seems to be operating but the temperature in the oven cavity is 
lower or higher than preset one. 
Grill heating element does operate.
Oven goes into cook cycle but shuts down before end of cooking cycle.
Oven seems to be operating but little or no heat is produced in oven 
load. (Microwave power does not seem to be generated properly)
Oven seems to be operating but the temperature in the oven cavity is 
lower or higher than preset one. 
Top and Bottom Grill heating elements do not heat.
Top or Bottom Grill heating element does not heat.
OFF
CONDITION
COOKING
CONDITION
(COMMON MODE)
MICROWAVE
COOKING
CONDITION
GRILL COOKING
CONDITION
CONVECTION
COOKING
CONDITION
DUAL COOKING
CONDITION
(COMMON MODE)
DUAL COOKING
CONDITION
(MICRO./CONV.)
DUAL COOKING
CONDITION
(MICRO./GRILL)
CONDITION 
PROBLEM
BLOCKED COOLING FAN
BLOCKED CONVECTION FAN
NO POWER AT WALL OUTLET
HOME FUSE OR BREAKER
MIS-ADJUSTMENT OF SWITCHES
BLOCKED VENTILATION OPENINGS
OPENED WIRE HARNESS
SHORTED WIRE HARNESS
OVEN LAMP OR SOCKET
POWER SUPPLY CORD
FOIL PATTERN ON P.W.B.
RELAY RY7
RELAY RY6
RELAY RY5
RELAY RY4
RELAY RY3
RELAY RY2
RELAY RY1
KEY UNIT
TOUCH CONTROL PANEL
TC TRANSFORMER
BTTOM GRILL HEATING ELEMENT
TOP GRILL HEATING ELEMENT
FUSE F8A
FUSE 20A
NOISE FILTER
CONVECTION FAN MOTOR
FAN MOTOR
TURNTABLE MOTOR
THERMAL CUT-OUT 145˚C (OVEN)
THERMAL CUT-OUT 125˚C (MG) 
THERMISTOR
MONITOR SWITCH
STOP SWITCH
MONITORED LATCH SWITCH
HIGH VOLTAGE CAPACITOR
H.V. HARNESS
H.V. RECTIFIER ASSEMBLY
HIGH VOLTAGE  TRANSFORMER
MAGNETRON
 
E E E 
H
TEST PROCEDURE
POSSIBLE CAUSE
AND
DEFECTIVE PARTS
 
M N 
O O O O O 
O O 
P
Q
TROUBLESHOOTING GUIDE
R-895M - 13
A
MAGNETRON TEST
CARRY OUT 3D CHECKS.
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 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
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 IEC-60705 procedure must be carried out using laboratory-type procedures and equip-
ment.
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 IEC705
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 36 seconds on full power.
NOTE: The operation time of the microwave oven includes "3" sec. (3 sec. is magnetron filament
heat-up time.)
4. When the 1 minute and 36 seconds is completed, remove the  container and stir the water. Note
temperature as T2.
5. Calculate the output power using the following formula:
R.F. Power Output = (T2 - T1) x 90.
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
NEVER TOUCH ANY PART IN THE CIRCUIT WITH YOUR HAND OR AN INSULATED TOOL
WHILE THE OVEN IS IN OPERATION.
PROCEDURE
LETTER
COMPONENT TEST
TEST PROCEDURES
R-895M - 14
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 B+C 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 kΩ in the other direction.
CARRY OUT 4R CHECKS.
ASYMMETRIC RECTIFIER TEST
CARRY OUT 3D CHECKS.
Isolate the high voltage rectifier assembly from the HV circuit. The asymmetric rectifier can be tested
using an ohmmeter set to its highest range across the terminals A+B of the asymmetric rectifier and
note the reading obtained. Reverse the meter leads and note this second reading. If an open circuit is
indicated in both directions then the asymmetric rectifier is good. If the asymmetric rectifier is shorted
in either direction, then the asymmetric rectifier is probably faulty and must be replaced with high voltage
rectifier. When the asymmetric rectifier is defective, check whether magnetron, high voltage rectifier,
high voltage wire or filament winding of the high voltage transformer is shorted.
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.
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 ................................ approximately 1.9 Ω
b. Secondary winding .......................... approximately 124 Ω
c. Filament winding .........................................  less than 1 Ω
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.
D2
D1
ASYMMETRIC
RECTIFIER
HIGH VOLTAGE RECTIFIER
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 10MΩ
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 MΩ  because of its internal 10MΩ
resistance.
F. When the internal wire is opened in the high voltage 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
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.
TEST PROCEDURES
B
HIGH VOLTAGE  TRANSFORMER TEST
PROCEDURE
LETTER
COMPONENT TEST
R-895M - 15
If incorrect readings are obtained, replace the motor.
CARRY OUT 4R CHECKS.
CARRY OUT 3D CHECKS.
Disconnect the leads from the terminals of the thermal cut-out. Then using an ohmmeter, make a
continuity test across the two terminals as described in the below.
Table: Thermal Cut-out Test
Temperature of "ON"
Temperature of "OFF"
Indication of ohmmeter
        Parts Name
 condition  (closed circuit).
condition (open circuit). (When room temperature
(˚C)
(˚C)
is approx. 20˚C.)
Thermal cut-out 125˚C
This is not resetable
Above 125˚C
Closed circuit
Thermal cut-out 145˚C
Below 115˚C.
Above 145˚C
Closed circuit
If incorrect readings are obtained, replace the thermal cut-out.
An open circuit thermal cut-out (MG) indicates that the magnetron has overheated, this may be due to
resistricted ventilation, cooling fan failure.
An open circuit thermal cut-out (OVEN) indicates that the oven cavity has overheated, this may be due
to no load operation,or excessive heat / fire inside the oven.
CARRY OUT 4R CHECKS.
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,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.
F
THERMISTOR TEST
CARRY OUT 3D CHECKS.
Disconnect the connector B from CPU unit. Measure the resistance of the thermistor with an
ohmmeter. Connect the ohmmeter leads to Pin No's C1 and C3 of the thermistor harness.
Room Temperature
Resistance
20˚C - 30˚C
Approximately 359.9 kΩ - 152 kΩ
If the meter does not indiicate above resistance, replace the thermistor.
CARRY OUT 4R CHECKS.
PROCEDURE
LETTER
COMPONENT TEST
G
THERMAL CUT-OUT TEST
H
MOTOR WINDING TEST
CARRY OUT 3D CHECKS.
Disconnect the leads from the motor. Using an ohmmeter, check the resistance between the two
terminals as described in the table below.
Table: Resistance of Motor
Motors
Resistance
Fan motor
Approximately
293 Ω
Turntable motor
Approximately
15 kΩ
Convection fan motor
Approximately
288 Ω
TEST PROCEDURES
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Sharp R-895M (serv.man6) Service Manual ▷ Download

  • DOWNLOAD Sharp R-895M (serv.man6) Service Manual ↓ Size: 483 KB | Pages: 7 in PDF or view online for FREE
  • Here you can View online or download the Service Manual for the Sharp R-895M (serv.man6) in PDF for free, which will help you to disassemble, recover, fix and repair Sharp R-895M (serv.man6) Microwave Oven. Information contained in Sharp R-895M (serv.man6) Service Manual (repair manual) includes:
  • Disassembly, troubleshooting, maintenance, adjustment, installation and setup instructions.
  • Schematics, Circuit, Wiring and Block diagrams.
  • Printed wiring boards (PWB) and printed circuit boards (PCB).
  • Exploded View and Parts List.