Sharp R21JCA - Commercial Microwave Oven, Supplemental Service Manual, Page: 7 / 24

5
R-21JCA
SCHEMATIC
NOTE: CONDITION OF OVEN
1. LIGHT UP DIAL OFF.
2. DOOR CLOSED.
Figure O-1 Oven Schematic-OFF Condition
NOTE: Indicates components with potential above 250 V.
OL FM AM
OVEN
LAMP FAN
MOTOR ANTENNA
MOTOR
AC120V
60 Hz
MONITOR
FUSE 20A
POWER
TRANSFORMER
CAPACITOR
0.94
µ
F
2400V
DOOR SENSING
SWITCH
SECONDARY
INTERLOCK SWITCH
CONTROL UNIT
THERMAL
CUT-OUT
125˚C (OVEN) THERMAL
CUT-OUT
145˚C (MAG.)
PRIMARY INTERLOCK RELAY
COOK RELAY
MONITOR SWITCH
MAGNETRON
RECTIFIER
RY1 RY2
A5
A3 A1
TEST PROCEDURES
PROCEDURE
LETTER
COMPONENT TEST
I CONTROL PANEL ASSEMBLY TEST
WARNING : To prevent an electric shock do not touch the electrical parts and the printed wiring
board. Because the control unit is "TRANSLESS CIRCUIT" and many electrical parts
are used at A.C. line voltage.
The 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 troubleshooting by unit replacement is described
according to the symptoms indicated.
Before testing,
1) Disconnect the power supply cord and then remove outer case.
2) Open the door and block it open.
3) Discharge high voltage capacitor.
4) Disconnect the leads to the primary of the power transformer.
5) Ensure that these leads remain isolated from other components and oven chassis by using
insulation tape.
6) After that procedure, re-connect the power supply cord.
1. Control Panel
The following symptoms indicate a defective control unit.
1-1 In connection with LEDs
a) At a certain LED, all or some LEDs do not light up.
b) At a certain LED, brightness is low.
c) Only one LED does not light up.
d) All or some LEDs continue to light up.
e) A certain group of LEDs do not light up.
f) The LEDs flicker.