Sharp R-872M Service Manual page 14

TEST PROCEDURES
PROCEDURE
LETTER
I NOISE FILTER TEST
CARRY OUT 3D CHECKS.
Disconnect the leads from the terminals of noise filter.
Using an ohmmeter, check between the terminals as
described in the following table.
If incorrect readings are absorbed, replace the noise filter unit.
CARRY OUT 4R CHECKS.
J BLOWN FUSE 15A
CARRY OUT 3D CHECKS.
If the fuse15A 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:
K BLOWN FUSE F8A
CARRY OUT 3D CHECKS.
1. If the fuse F8A is blown when the door is opened, check the monitored latch switch and monitor
switch.
2. If the fuse F8A is blown by incorrect door switching replace the defective switch(es) and the fuse
F8A.
3. If the fuse F8A is blown, there could be shorts in the asymmetric rectifier or there is a ground in wire
harness. A short in the asymmetric rectifier may be occurred due to short or ground in H.V. rectifier,
magnetron, high voltage transformer or H.V. wire. Check them and replace the defective parts or
repair the wire harness.
CARRY OUT 4R CHECKS.
CAUTION:
L GRILL HEATING ELEMENT (TOP) AND BOTTOM HEATING ELEMENTS TEST
CARRY OUT 3D CHECKS.
Before carrying out the following tests make sure the heating element is cool completely.
1. Resistance of heating element.
Disconnect the wire leads to the heating element to be tested. Using ohmmeter with low resistance
range. Check the resistance across the terminals of the heating element as described in the
following table.
2. Insulation resistance.
Disconnect the wire leads to the heating element to be tested. Check the insulation resistance
between the element terminal and cavity using a 500V - 100MΩ insulation tester. The insulation
resistance should be more than 10 MΩ in the cold start.
If the results of above test 1 and/or 2 are out of above specifications, the heating element is probably
faulty and should be replaced.
CARRY OUT 4R CHECKS.
MEASURING POINTS
Between N and L
Between terminal N and WHITE
Between terminal L and RED
with the correct value replacement.
Only replace fuse
Only replace fuse F8A with the correct value replacement.
Table: Resistance of heating element
Parts name
Grill heating element (top)
Bottom heating element
R-872M - 14
COMPONENT TEST
L
15A
Cx
N
F8A
Cx ± 20% Cy ± 20%
L (min)
1.0mH 0.22µF 4700pF
INDICATION OF OHMMETER
Approx. 680 kΩ
Short circuit
Short circuit
Resistance
Approximately 61 Ω
Approximately 115 Ω
WHT
L
R1
L
RED
R2 Cy
R1 R2
10 MΩ 680kΩ