Sharp R-1900J, Service Manual

Page: 10 / 52

R1900J
5 – 1
R1900J
Service Manual
CHAPTER 5.
TROUBLESHOOTING GUIDE
When troubleshooting the microwave oven, it is helpful to follow the Sequence of Operation in performing the checks. Many of the possible causes of
trouble will require that a specific test be performed. These tests are given a procedure letter which will be found in the “Test Procedure“ section.
IMPORTANT:
If the oven becomes inoperative because of a blown weak point (1) or (2), check the monitor switch (1) or (2), primary interlock relay RY1, door sens-
ing switch and secondary interlock switch (1) or (2), before replacing the weak point (1) or (2).
Never touch any part in the circuit with your hand or an uninsulated tool while the power supply is connected.
Home
fuse
blows
when
power
cord
is
plugged
into
wall
receptacle
"
.
"
does
not
appear
in
display
when
power
cord
is
first
plugged
into
wall
receptacle.
Oven
lamp
does
not
g
o
o
n
for
1
m
inute
a
fter
door
is
opened.
Oven
lamp
and
antenna
motors
d
o
not
go
on
in
cook
cycle.
Fan
motor
does
not
operate.
Exhaust
fan
does
not
operate.
Exhaust
motor
does
not
operate.
OFF CONDITION CONDITION
PROBLEM
COOKING CONDITION
POSSIBLE
CAUSE
A
ND
DEFECTIVE
PARTS
TEST
P
ROCEDURE
MAGNETRON(1), (2)
POWERTRANSFORMER (1),(2)
H.V.RECTIFIER ASSEMBLY(1), (2)
HIGHV OLTAGECAPACITOR (1),(2)
SECONDARYINTERLOCK SWITCH (1),(2)
PRIMARYINTERLOCK SYSTEM
DOORSENSING SWITCH
MONITORSWITCH (1),(2)
WEAKPOINT (inNoise filter)
MAGNETRONTEMP. FUSE(1), (2)
OVENTEMPERATURE FUSE
OVENLAMP ORSOCKET
FANMOTORS
EXHAUSTFAN
EXHAUSTMOTOR
WEAKPOINT (1),(2)
WEAKPOINTS (forFan motors)
WEAKPOINT (forExhaust fanm otor)
EXHAUSTTHERMISTOR
MAGNETRONTHERMISTOR
NOISEFILTER
KEYUNITS
POWERUNIT
RELAYUNIT
CONTROLUNIT
SWITCHUNIT.
AIRFLOW BLOCKED
LOOSEWIRING
SHORTIN POWERSUPPLY CORD
NOPOWER ATOUTLET
LOWPOWER SUPPLYVOLTAGE
AB
C
D
E
F
F
G
J
KK
H
I
I
M
L
O
Q
R
P
N
Weak
point
(in
noise
filter)
blows
when
pow-
er
cord
is
plugged
into
wall
receptacle.
Oven
doen
not
g
o
into
c
ook
c
ycle
w
hen
START
pad
on
the
door
is
touched.
Oven
does
not
g
o
into
c
ook
cycle
when
START
pad
is
touched.
Variable
cooking
does
not
o
perates
proper
-
ly
,
e
xc
e
p
t
H
IG
H
power
functions.
Low
or
no
power
is
produced
during
cook
-
ing
condition.
(The
food
is
heated
incom
-
pletely
or
not
heated
at
all.)
Oven
goes
into
a
cook
cycle
b
ut
shuts
d
own
before
and
off
cooking
cycle.
It
seems
that
the
o
utput
power
is
low
-
er
or
higher
than
the
rated
one.