Sharp R-254M (serv.man5) Service Manual ▷ View online
R-254M - 25
MICROWAVE MEASUREMENT
After any repair, the microwave oven must be checked for
microwave leakage to ensure continued safe operation.
BS EN 60335-2-25 specifies that the maximum permitted
leakage with a load of 275 ml is 50 W/m
microwave leakage to ensure continued safe operation.
BS EN 60335-2-25 specifies that the maximum permitted
leakage with a load of 275 ml is 50 W/m
2
(equivalent to 5
mW/cm
2
)
at a distance of 5 cm from the oven.
PREPARATION
The following items are required to carry out this test:-
1. A low form of 600 ml beaker made from an electrically
1. A low form of 600 ml beaker made from an electrically
non-conductive material, such as glass or plastic, with
an inside diameter of approximately 8.5 cm. This must
contain 275
an inside diameter of approximately 8.5 cm. This must
contain 275
±
15 ml of water, at an initial temperature
of 20
±
2˚C.
2. A leakage detector which has been calibrated within
the preceding 12 months to a stand whose accuracy
can be traced to National Physical Laboratory Stand-
ards.
can be traced to National Physical Laboratory Stand-
ards.
Recommended instruments are:
Apollo "XI"
Celtec "A100"
Celtec "A100"
Before commencing the test, check that the leakage
detector is functioning and adjusted according to the
manufacturer's instructions, and any spacers are fitted to
ensure that measurement is taken 5cm from the surface of
the oven.
detector is functioning and adjusted according to the
manufacturer's instructions, and any spacers are fitted to
ensure that measurement is taken 5cm from the surface of
the oven.
PROCEDURE
1. Place the beaker containing the water load in the oven
cavity at the centre of the turntable. The placing of this
standard load in the oven is important, not only to
protect the oven, but also to ensure that any leakage
it is not disguised by too large a load absorbing energy.
standard load in the oven is important, not only to
protect the oven, but also to ensure that any leakage
it is not disguised by too large a load absorbing energy.
2. Close the oven door, and with the power level set to
FULL, turn the oven ON with the timer set for a few
minutes operation. Should the water begin to boil
before the test has been completed, it should be
replaced.
minutes operation. Should the water begin to boil
before the test has been completed, it should be
replaced.
3. As shown in the diagram below, move the probe slowly
(not faster than 2.5 cm/sec.);-
a) around the edge of the door following the gap
b) across the face of the door
c) across any vents in the oven's sides, rear or top
b) across the face of the door
c) across any vents in the oven's sides, rear or top
Dotted line indicates the path taken by the leakage detector.
Whilst the maximum leakage permitted in BS EN 60335-2-25 is 50 W/m
2
(equivalent to 5 mW/cm
2
), it is not normal
to detect any significant leakage, and therefore any detected leakage should be investigated.
R-254M - 26
NOTE: " " indicates components with potential above 250V.
SCHEMATIC
NOTE: CONDITION OF OVEN
1. DOOR CLOSED.
2. CLOCK OR " : " APPEARS ON DISPLAY.
1. DOOR CLOSED.
2. CLOCK OR " : " APPEARS ON DISPLAY.
SCHEMATIC
NOTE: CONDITION OF OVEN
1. DOOR CLOSED.
2. MICROWAVE POWER LEVEL HIGH.
3. COOKING TIME ENTERED.
4. START PAD TOUCHED.
1. DOOR CLOSED.
2. MICROWAVE POWER LEVEL HIGH.
3. COOKING TIME ENTERED.
4. START PAD TOUCHED.
Figure O-2 Oven Schematic-ON Condition
Figure O-1 Oven Schematic-OFF Condition
SCHEMATIC DIAGRAMS
FAN MOTOR
*
POWER TRANSFSORMER WITH 150 C
RY3
RY1
COM.
NO.
NO.
COM.
A3
A1
CONTROL UNIT
STOP
SWITCH
B2
B1
G-Y/18
/18
/18
L
N
BRN
BLU
EARTH
NOISE FILTER
UNIT
FM
TT
M
230-240V 50Hz
THERMOSTAT IN PRIMARY WINDING
*
CAPACITOR
0.88 F
*
H.V.
RECTIFIER
THERMAL
CUT-OUT
OVEN
125 C
F1
*
MAGNETRON
NO
COM
NC
NOISE SUPPRESSION COIL
2100VAC
TURNTABLE
MOTOR
680k /0.5W
0.0033 F/250V
0.22 F/250V
10M /0.5W
0.0033 F/250V
OL
LIGHT
OVEN
NO
COM
SWITCH
MONITOR
MONITORED
LATCH
SWITCH
SW3
SW1
SW2
FAN MOTOR
*
POWER TRANSFSORMER WITH 150 C
RY3
RY1
COM.
NO.
NO.
COM.
A3
A1
CONTROL UNIT
STOP
SWITCH
B2
B1
G-Y/18
/18
/18
L
N
BRN
BLU
EARTH
NOISE FILTER
UNIT
FM
TT
M
230-240V 50Hz
THERMOSTAT IN PRIMARY WINDING
*
CAPACITOR
0.88 F
*
H.V.
RECTIFIER
THERMAL
CUT-OUT
OVEN
125 C
F1
*
MAGNETRON
NO
COM
NC
NOISE SUPPRESSION COIL
2100VAC
TURNTABLE
MOTOR
680k /0.5W
0.0033 F/250V
0.22 F/250V
10M /0.5W
0.0033 F/250V
OL
LIGHT
OVEN
NO
COM
SWITCH
MONITOR
MONITORED
LATCH
SWITCH
SW3
SW1
SW2
R-254M - 27
Figure S-1. Pictrorial Diagram
HIGH VOLTAGE COMPONENTS
MONITORED
LATCH SWITCH
MONITOR
SWITCH
TURNTABLE
MOTOR
COM.
COM.
BLK
N
L
WHT
RED
WHT
BLK
N.C.
STOP SWITCH
WHT
RED
RED
WHT
WHT
RED
GRN
WHT
RED
G/Y
BLK
RED
BLK
BLU
BRN
RED
RED
THERMAL CUT-OUT
(OVEN)
OVEN
LAMP
BLK
BLK
BLK
BLK
RED
WHT
CN-A
CN-B
2
BLK
1
1
3
WHT
WHT
WHT
WHT
WHT
GRN
GRN
RED
GRN
2
1
N.O.
COM.
N.O.
FAN MOTOR
NOISE FILTER
H.V.WIRE B
MAGNETRON
H.V.
CAPACITOR
H.V.
RECTIFIER
HIGH VOLTAGE
TRANSFORMER
POWER SUPPLY CORD
LIVE
NEUTRAL
WHT
BLK
WHT
RY3
RY1
CN-A
T1
3
1
2
1
CONTROL UNIT
IC1
CN-B
CN-G
CN-C
CN-C
PICTORIAL DIAGRAM
R-254M - 28
Figure S-2. Power Unit Circuit
POWER UNIT CIRCUIT DIAGRAM
+
–
B 1
C 1
C 2
C 3
C 4
C 6
C 7
C 5
C 8
C 9
C10
C11
C12
C13
B 2
A 1
A 3
NO
COM
NO
COM
STOP
SWITCH
SWITCH
STOP
SWITCH
SWITCH
NC
GND
VC
BUZZER
VR
INT
CN-C
13 WIRE HARNESS
AC230-240V
50Hz
50Hz
OVEN LAMP
TURNTABLE
MOTOR
FAN MOTOR
TURNTABLE
MOTOR
FAN MOTOR
HIGH
VOLTAGE
TRANSFORMER
VOLTAGE
TRANSFORMER
R3
130 1w
130 1w
D1
S1NB10
S1NB10
R1 430 2w
R2 470 1w
T1
1
6
3
4
GND
a
b
c
d
VRS1
C1 470
µ
/50v
SP1
(J1)
10G471K
RY1
RY3
CN-B
CN-A
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