Read Sharp R-750AM (serv.man2) Service Manual online
5
750A -
PROCEDURE
LETTER
COMPONENT TEST
C
RELAY TEST
1. CARRY OUT 3D CHECKS.
2. Disconnect the leads from the primary of the high voltage transformer. Make sure that the leads remain
2. Disconnect the leads from the primary of the high voltage transformer. Make sure that the leads remain
isolated from other oven components and chassis. (Use insulation tape if necessary.)
3. Close the door.
4. Reconnect the supply.
5. Check the voltage between Pin Nos. 1 and 3 of the 3 pin connector (A) on the control unit with an A.C.
4. Reconnect the supply.
5. Check the voltage between Pin Nos. 1 and 3 of the 3 pin connector (A) on the control unit with an A.C.
voltmeter. The meter should indicate 240 volts, if not check oven circuit.
6. RY1, RY2 and RY3 TEST
These are operated by D.C. voltage. Check voltage at the relay coil with a D.C. voltmeter during the
These 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,
DC. voltage not indicated ........ Check diode which is connected to the relay coil. If diode is good,
control unit is defective.
RELAY SYMBOL
OPERATIONAL VOLTAGE
CONNECTED COMPONENTS
RY1
APPROX. 25.0V D.C.
Oven lamp / Turntable motor / Cooling fan motor
RY2
APPROX. 25.0V D.C.
Grill heater
RY3
APPROX. 25.0V D.C.
High voltage transformer
D
PROCEDURES TO BE TAKEN WHEN THE FOIL PATTERN ON THE PRINTED WIRING
BOARD(PWB) IS OPEN
BOARD(PWB) IS OPEN
NOTE: *At the time of these repairs, make a
visual inspection of the varistor for burn-
ing damage and examine the transformer
with tester for the presence of layer short-
circuit (check primary coil resistance). If
any abnormal condition is detected, re-
place the defective parts.
ing damage and examine the transformer
with tester for the presence of layer short-
circuit (check primary coil resistance). If
any abnormal condition is detected, re-
place the defective parts.
CARRY OUT 4R CHECKS.
To protect the electronic circuits, this model is provided with a fine foil pattern added to the primary on
the PWB, this foil pattern acts as a fuse. If the foil pattern is open, follow the troubleshooting guide
given below for repair.
the PWB, this foil pattern acts as a fuse. If the foil pattern is open, follow the troubleshooting guide
given below for repair.
Problem: POWER ON, indicator does not light up.
CARRY OUT 3D CHECKS.
STEPS
OCCURANCE
CAUSE OR CORRECTION
1
The rated AC voltage is not present at
Check supply voltage and oven power cord.
POWER terminal of CPU connector (CN-A).
2
The rated AC voltage is present at primary
Low voltage transformer or secondary circuit defective.
side of low voltage transformer.
Check and repair.
3
Only pattern at "a" is broken.
*Insert jumper wire J1 and solder.
(CARRY OUT 3D CHECKS BEFORE REPAIR)
4
Pattern at "a" and "b" are broken.
*Insert the coil RCILF2003YAZZ between "c" and "d".
(CARRY OUT 3D CHECKS BEFORE REPAIR)
RY2
OL / FM
/ TTM
/ TTM
AC
5
1
D20
VRS1
a
b
d
c
CN - A
D21
RY1
(J1)
T1
TEST PROCEDURES
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