R-291KM - Sharp Home Appliance Service Manual (repair manual)

R-291(K)M

CONTENTS

SX402R291PKW

In the interest of user-safety the oven should be restored to its 
original condition and only parts identical to tho
should be used.

CONTENTS

CHAPTER 1. BEFORE SERVICING 
[1]  GENERAL IMPORTANT INFORMATION................1-1
[2]  CAUTION MICROWAVE RADIATION .....................1-1
[3] WARNING .....................................................................1-1

CHAPTER 4. APPEARANCE VIEW
[1] OVEN ..............................................................................4-1
[2]  TOUCH CONTROL PANEL.........................................4-1

CHAPTER 5. OPERATION SEQUENCE
[1] OFF 

CONDITION .........................................................5-1

[2] MICROWAVE 

COOKING 

CONDITION ...................5-1

[3]  SENSOR COOKING CONDITION..............................5-2

CHAPTER 6. FUNCTION OF IMPORTANT COMPO-
NENTS
[1]  DOOR OPEN MECHANISM.....................................6-1
[2]  DOOR SENSING SWITCH AND SECONDARY 
          INTERLOCK SWITCH.....................................................6-1
[3] MONITOR 

SWITCH 

.....................................................6-1

[4] FUSE 

T6.3A .................................................................6-1

[5] HIGH 

VOLTAGE 

FUSE 

.................................................6-1

[6]  TEMPERATURE FUSE 150C (OVEN) .......................6-1
[7] TURNTABLE 

MOTOR ................................................6-1

[8] FAN 

MOTOR .................................................................6-1

[9] HUMIDITY 

SENSOR......................................................6-1

[10]   NOISE FILTER ................................................................6-1

CHAPTER 7. TROUBLESHOOTING GUIDE
[1] FOREWORD ..................................................................7-1
[2] CHART ............................................................................7-1

CHAPTER 8. TEST PROCEDURES
[1]  Procedure A: MAGNETRON (MG) TEST...............8-1
[2]  Procedure B: HIGH VOLTAGE TRANS-

FORMER TEST ..............................................................8-2

[3] Procedure C: HIGH VOLTAGE RECTIFI-

ER TEST ..........................................................................8-2

[4]  Procedure D: HIGH VOLTAGE CAPACI-

TOR TEST .......................................................................8-2

[5]  Procedure E: SWITCH TEST .....................................8-2
[6]  Procedure F: TEMPERATURE FUSE 

TEST ...............................................................................8-3

[7]  Procedure G: MOTOR WINDING TEST.................8-3
[8]  Procedure H: FUSE T6.3A ........................................8-3
[9]  Procedure I: HIGH VOLTAGE FUSE TEST ..............8-3
[10]  Procedure J: TOUCH CONTROL PANEL 
          ASSEMBLY TEST...........................................................8-4
[11]  Procedure K: KEY UNIT (MEMBRANE SWITCH) 
          TEST..................................................................................8-4
[12]  Procedure L: RELAY TEST..........................................8-5

[13]  Procedure M: PROCEDURES TO BE TAKEN 
          WHEN THE THERMAL FUSE IN LOW VOLTAGE 
          TRANSFORMER ON THE PRINTED WIRING
          BOARD (PWB) IS OPEN...............................................8-5

[1]  OUTLINE OF TOUCH CONTROL PANEL..................9-1
[2]  PRECAUTIONS FOR USING LEAD-FREE SOLDER.9-1
[3]  SERVICE FOR TOUCH CONTROL PANEL..........................9-2

ADJUSTMENT PROCEDURE
[1] BEFORE 

OPERATING ................................................... 10-1

[2]  OUTER CASE REMOVAL ............................................. 10-1
[3] HIGH 

VOLTAGE 

TRANSFORMER 

RE-

MOVAL ........................................................................... 10-2

[4] 

HIGH VOLTAGE RECTIFIER ASSEMBLY, 

HIGH VOLTAGE FUSE AND HIGH VOLT-
AGE CAPACITOR REMOVAL .................................... 10-2

[5] MAGNETRON 

REMOVAL .......................................... 10-2

[6]  POSITIVE LOCK CONNECTOR (NO-

CASE TYPE) REMOVAL ...............................................10-2

[7] TURNTABLE 

MOTOR 

REMOVAL ................................10-3

[8] COOLING 

FAN 

MOTOR 

REMOVAL...........................10-3

[9]  POWER SUPPLY CORD REPLACE-

MENT.................................................................................10-4

[10] CONTROL PANEL ASSEMBLY REMOV-

AL .....................................................................................10-4

[11]  GRAPHIC SHEET AND MEMBRANCE SWITCH 
          REPLACEMENT...............................................................10-4
[12] DOOR SWITCH, SECONDARY INTERLOCK 
          SWITCH AND MOTOR SWITCH REMOVAL............10-5
[13]  DOOR SWITCH, SECONDARY INTERLOCK 
          SWITCH AND MOTOR SWITCH ADJUSTMENT.....10-5
[14] DOOR REPLACEMENT..................................................10-5

CHAPTER 12. CIRCUIT DIAGRAMS
[1] Oven 

Schematic ........................................................ 12-1

[2] Pictorial 

Diagram 

(Figure 

S-1)

[3]     Control unit circuit (Figure S-2)............................ 12-3
[4]     Control unit circuit (Figure S-3)............................ 12-4
[5]     Printed Wiring Board (Figure S-4)........................ 12-5

.............................. 12-2

R-291(K)M

R-291(K)M

1 – 1

R218L(W)

This Manual has been prepared to provide Sharp Corp. Service engineers with Operation and Service Information.

isfactory customer ser-

vice.   

Service engineers should not be exposed to the microwave energy which may radiate from the magnetron or other
microwave generating devices if it is improperly used or connected. All input and output microwave connections,

ts must be secured. Never operate the device without a microwave energy absorbing

load attached. Never look into an open wave guide or antenna while the device is energized.

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 not any other visible damage with the oven.

Servicing and repair work must be carried out only by trained service engineers.

All the parts marked "

" on parts list are used at voltages more than 250V.

Removal of the outer wrap gives access to potentials above 250V.

All the parts marked "*" on parts list may cause undue microwave exposure, by themselves, or when they are damaged,
loosened or removed.

                 THE WIRES IN THIS MAINS LEAD ARE COLOURED IN ACCORDANCE WITH THE FOLLOWING CODE:
                                           

                     

GREEN-AND-YELLOW --------------EARTH

                                             

                         BLUE -----------------------------------NEUTRAL

                                              

                        BROWN ---------------------------------------LINE

R-291(K)M

2 – 1

R218L(W)

Microwave ovens contain circuitry capable of producing very high voltage and current, contact with any part of the high voltage circuit will result in

ltage harness.

1) Disconnect the supply.

2) Door opened, and wedged open.

3) Discharge the high voltage capacitor.

WARNING: AGAINST THE CHARGE OF THE HIGH-VOLTAGE

CAPACITOR

The high-voltage capacitor remains charged about 60 sec-

onds and then short-circuit the connection of the high-
voltage capacitor (that is, of the connecting lead of the

an insulated screwdriver. 

out

with the supply disconnected. It may, in some cases, be necessary to
connect the supply after the outer case has been removed, in this
event carry out 3D checks and then disconnect the leads to the pri-
mary of the power transformer. Ensure that these leads remain iso-
lated from other components and the oven chassis. (Use insulation
tape if necessary.) When the testing is completed, carry out 3D  checks
and reconnect the leads to the primary of the power transformer.

1) Reconnect all leads removed  from components during testing.

2) Replace the outer case (cabinet).

3) Reconnect the supply.

4) Run the oven. 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 level to HIGH
(100%). And set the microwave timer for two (2) minutes. When the
two minutes has elapsed (timer at zero) carefully check that the water
is now hot. If the water remains cold, carry out 3D checks 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 microwave leakage test
should be carried out.