R-27STMA (serv.man8). Test Procedures - Sharp Home Appliance Service Manual (repair manual)

r-27stma (serv.man8) service manual
Model
R-27STMA (serv.man8)
Pages
4 Few pages! See other manuals at the bottom of the first or last page.
Size
179.66 KB
Type
PDF
Document
Service Manual
Brand
Device
Home Appliance / Microwave Oven / Test Procedures
File
r-27stma-sm8.pdf
Date

Read Sharp R-27STMA (serv.man8) Service Manual online

R27STMA
8 – 1
R27STMA
Service Manual
 
CHAPTER 8. 
TEST PROCEDURES
[1] A: MAGNETRON TEST
1. CARRY OUT 3D CHECKS.
2. 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.
3. 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.
4. Reconnect all leads removed from components during testing.
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.
1. MICROWAVE OUTPUT POWER
The following test procedure should be carried out with the microwave oven in a fully assembled condition (outer case fitted).
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%).
2. 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 Techni-
cal Training notes (part number SERV-LITMW01). The maximum leakage permitted in BS EN 60335-2-25 is 50W/m
2
 (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
[2] B: HIGH VOLTAGE TRANSFORMER TEST
1. CARRY OUT 3D CHECKS.
2. 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 -------------------- 2.6 ohms approximately
                  b.Secondary winding --------------- 199 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.
3. CARRY OUT 4R CHECKS.
 NEVER TOUCH ANY PART IN THE CIRCUIT WITH YOUR HAND OR AN INSULATED TOOL WHILE THE OVEN IS IN OPERATION.
WARNING: High voltages and large currents are present at the secondary winding and filament winding of the power transformer. It is 
very dangerous to work near this part when the oven is on. NEVER make any voltage measurements of the high-voltage cir-
cuits, including the magnetron filament.
R27STMA
8 – 2
[3] 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 k
Ω 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 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.
[4] D: HIGH VOLTAGE CAPACITOR TEST
CARRY OUT 3D CHECKS.
1. Isolate the high voltage capacitor from the circuit.
2. Continuity check must be carried out with measuring instrument which is set to the highest resistance range.
3. A normal capacitor shows continuity for a short time (kick) and then a resistance of about 10M
Ω after it has been charged.
4. A short-circuited capacitor shows continuity all the time.
5. An open capacitor constantly shows a resistance about 10 M
Ω because of its internal 10MΩ resistance.
6. When the internal wire is opened in the high voltage capacitor shows an infinite resistance.
7. 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.
[5] E: SWITCH TEST
CARRY OUT 3D CHECKS.
Isolate the switch to be tested and using an ohmmeter check between the terminals as described in the following table.
If incorrect readings are obtained, make the necessary switch adjustment or replace the switch.
CARRY OUT 4R CHECKS.
[6] F: TEMPERATURE FUSE TEST
CARRY OUT 3D CHECKS.
Disconnect the leads from the terminals of the temperature fuse. Then using an ohmmeter, make a continuity test across the two terminals as
described in the below.
If incorrect readings are obtained, replace the temperature fuse.
An open circuit temperature fuse (OVEN) indicates that the food in the oven cavity may catch fire, this may be due to overheating produced by
improper setting of the cooking time or failure of the control panel.
CARRY OUT 4R CHECKS.
Table: Terminal Connection of Switch
Plunger Operation
COM to NO
COM to NC
COM; Common terminal
Released
Open circuit
Short circuit 
NO;     Normally open terminal 
Depressed
Short circuit 
Open circuit.
NC;     Normally close terminal
Table: Temperature Fuse Test
Parts Name
Temperature of “ON” condition 
(closed circuit).
Temperature of “OFF” condition 
(open circuit).
Indication of ohmmeter (When room 
temperature is approx. 20
°C.)
Temperature fuse 150
°C
This is not resetable type.
Above 150
°C
Closed circuit
D2
D1
ASYMMETRIC
RECTIFIER
HIGH VOLTAGE
RECTIFIER
A
B
C
R27STMA
8 – 3
[7] G: 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.
If incorrect readings are obtained, replace the motor.
CARRY OUT 4R CHECKS.
[8] H: FUSE T6.3A
CARRY OUT 3D CHECKS.
If the fuse T6.3A is blown when the door is opened, check the secondary interlock switch, primary interlock relay (RY2) and monitor switch.
If the fuse T6.3A is blown by incorrect door switching replace the defective switch(es) and the fuse  T6.3A.
If the fuse T6.3A is blown, there is a shorts or grounds in electrical parts or wire harness. Check them and replace the defective parts or repair the
wire harness.
CARRY OUT 4R CHECKS.
CAUTION: ONLY REPLACE FUSE T6.3A WITH THE CORRECT VALUE REPLACEMENT.
[9] I: NOISE FILTER TEST
CARRY OUT 3D CHECKS.
Disconnect the leads from the terminals of the noise filter. Using an ohmmeter, check between the
terminals as described in the following table. 
If incorrect readings are obtained, replace the noise filter unit.
CARRY OUT 4R CHECKS.
[10] J: TOUCH CONTROL PANEL ASSEMBLY TEST
The touch control panel consists of circuits including semiconductors such as LSI, ICs, etc. Therefore, unlike conventional microwave ovens, proper
maintenance cannot be performed with only a voltmeter and ohmmeter. In this service manual, the touch control panel assembly is divided into two
units, Control Unit and Switch Unit, and also the Control Unit is divided into two units, CPU Unit and Power Unit, and troubleshooting by unit replace-
ment is described according to the symptoms indicated.
1. Switch Unit. Note: Check switch unit wire harness connection before replacement.
The following symptoms indicate a defective switch unit. Replace the switch unit.
1) When touching the buttons, a certain button produces no signal at all.
2) When touching the buttons, sometimes a button produces no signal.
3) When rotating the TIMER/WEIGHT knob, the cooking time or the weight can not be input.
2. Control Unit.
The following symptoms indicate a defective control unit. Before replacing the switch unit, perform the Switch unit test (Procedure L) to determine
if control unit is faulty. 
1) In connection with buttons.
a) When touching the buttons, a certain group of buttons do not produce a signal.                                                                                                                                                     
b) When touching the buttons, no buttons produce a signal.
2) In connection with indicators.
a) At a certain digit, all or some segments do not light up.
b) At a certain digit, brightness is low.
c) Only one indicator does not light up. 
d) The corresponding segments of all digits do not light up; or they continue to light up.
e) Wrong figure appears.
f) A certain group of indicators do not light up.
g) The figure of all digits flicker.
Table: Resistance of Motor
Fan Motors
Turntable motor
Part Code
RMOTEA405WRZZ
RMOTDA289WRZZ
RMOTDA173WRE0
RMOTDA253WRZZ
Resistance
Approximately 388
Ω
Approximately 13.5k
Ω Approximately 12.2kΩ
Approximately 14.5k
Ω
MEASURING POINT 
INDICATION OF OHMMETER
Between N and L 
Open circuit
Between terminal N and WHITE 
Short circuit
Between terminal L and RED 
Short circuit
RED
WHT
FUSE
T6.3A
N
L
NOISE SUPPRESSION COIL
NOISE FILTER
R27STMA
8 – 4
3) Other possible troubles caused by defective control unit.
a) Buzzer does not sound or continues to sound.
b) Clock does not operate properly.
c) Cooking is not possible.
[11] K: SWITCH UNIT TEST
1. CARRY OUT 3D CHECKS.
2. Isolate the switch unit with the control panel frame to be tested.
3. Using an ohmmeter and referring to the switch unit matrix indicated on the switch unit circuit, check the circuit between the pins of the switch unit
that correspond to the STOP button. When the button is pressed, the ohmmeter should indicate short circuit. When the button is released, the
ohmmeter should indicate open circuit. If incorrect readings are obtained, the switch unitbutton is faulty and must be replaced. About the other but-
tons, the above method may be used.
4. CARRY OUT 4R CHECKS.
[12] L: RELAY (RY2, RY5, RY6) TEST
CARRY OUT 3D CHECKS.
Remove the outer case and check voltage between the pin No. 3 and No. 5 of connector CN-A on the control unit with an A.C. voltmeter. The meter
should indicate 230 - 240 volts, if not check oven circuit.
Relay Test
These relays are operated by D.C. voltage
Check voltage at the relay coil with a D.C. voltmeter during the microwave cooking operation.
        DC. voltage indicated ................................... Defective relay.
        DC. voltage not indicated ............................. Check diode which is connected to the relay coil. If diode is good, control unit is defective.
CARRY OUT 4R CHECKS.
[13] M: PROCEDURES TO THE CONTROL UNIT
Problem: POWER ON, indicator does not light up.
CARRY OUT 3D CHECKS.
NOTE: At the time of these steps, make a visual inspection of the varistor for burned damage. And examine the transformer with a tester for the pres-
ence of layer short-circuit (check the primary coil resistance). If any abnormal condition is detected, replace the control unit.
CARRY OUT 4R CHECKS.
RELAY SYMBOL
OPERATIONAL VOLTAGE
CONNECTED COMPONENTS
RY5
Approx. 12.7V D.C.
Oven lamp / Turntable motor / Cooling fan motor
RY2
Approx. 11.7V D.C.
High voltage transformer
RY6
Approx. 12.7V D.C.
Touch control transformer
STEPS
OCCURRENCE
CAUSE OR CORRECTION
1
The rated AC voltage is not present between the Pin No. 3 and Pin No. 5 
of connector CN-A.
Check supply voltage and oven power cord.
2
The oven door is opened and closed. 
But the rated AC voltage is not present to primary side of low voltage 
transformer.
Check the secondary interlock switch. 
If the secondary interlock switch is normal, the fuse or the 
relay RY-6 is defective. 
Check and replace the control unit.
3
The rated AC voltage is present to primary side of low voltage trans-
former.
Low voltage transformer or secondary circuit defective.
Check and replace the control unit.
G2
H7(G3)
G4
H3
H4
H5
(G9)
H6
(G7)
(G5)
A
B
C SW100
C-1
C-2
C-3
B3
B2
B1
A7
A6
A5
A4
A3
(G8)
(G10)
< SW UNIT >
(C100)
(C101)
(R100)
(R101)
(c)
(b)
(a)
A2
A1
G6
WH-A
7pin HARNESS
WH-B
4pin HARNESS
WH-C
3pin WIRE HARNESS
(d)
(H8(G1))
(B4)
(a)
(b)
CHICKEN
QUARTERS
ROAST BEEF/
LAMB
START
AUTO MINUTE
AUTO
COOK
MEAT
JOINT
ROAST
POULITRY
POWER
LEVEL
ROAST
POAK
STOP
CEAR
WHOLE
POULTRY
(c)
SW1
SW2
SW3
SW4
SW5
SW6
SW7
SW8
SW9
SW10
Page of 4
Display

Download Sharp R-27STMA (serv.man8) Service Manual (Repair Manual)

Here you can read online and download Sharp R-27STMA (serv.man8) Service Manual in PDF. R-27STMA (serv.man8) service manual will guide through the process and help you recover, restore, fix, disassemble and repair Sharp R-27STMA (serv.man8) Microwave Oven. Information contained in service manuals typically includes schematics / circuit diagrams, wiring diagrams, block diagrams, printed wiring boards, exploded views, parts list, disassembly / assembly, pcb.