17
(1) Examine when the lamp is on, the glass tray is cycling, the
fan operating in normal:
Take off the cabinet, starting the oven, measure the plug of the
transformer with an avometer to see whether it is enough to
230V. If it is enough to 230V, then the secondary high voltage of
the transformer should be examined as FIG.5 – 3.
Measure it with the 2500V-alternating grade of model 500
avometer. One rod of the avometer connects the iron core of the
transformer, the other rod connects the secondary high voltage
plug (FIG.5 - 4). The avometer reading should be about 2100V
(when measure, be careful with the high voltage). If no voltage
at all, it indicates that the transformer has broken, and should be
replaced by a new one. If it is enough to 2100V, then check the
filament voltage of the transformer with alternating 10V grade of
an avometer, the value should be about 3.4V (FIG.5 - 5).
If there is no voltage at all, it indicates the transformer has
broken, and should be replaced by a new one. If it is enough to
3.4V, check the filament resistance of the magnetron, measure
the filament plug with the R×1 grade of a avometer (FIG.5 - 6). If
it is open – circuited, it indicates the magnetron has broken, and
should be replaced by a new one. It is normal if the resistance
very small. Then check whether the magnetron steel has
broken, if broken, replace with a new magnetron.
If there is no problem with the magnetron, check the high
voltage diode then. Measure the diode with R×10K grade of an
avometer, the “+” rod end of the avometer connect the cathode
of the diode, the “-” rod end of the avometer connect the anode
of the diode (FIG.5 - 7).
The avometer reading should be about 150 thousand ohms.
The change the rod to different electrode, the reading should be
“
∞
” . If the reading is very small, and near to short circuit, it
indicates the high voltage diode has been punctured, and
should be replaced by a new one.
If the high voltage diode is OK, then check the forwarding plug
of the transformer to see whether it is enough to 230V. If it is not
enough, check the micro – switch of the time and power
distributor. Connect the two rods of the avometer to the 1,2 place
of the timer with R×1K grade. It is normal if the reading is “0”
when at cut off condition. If the reading is “
∞
”, it indicates the
micro switch has broken, and the timer should be replaced by a
new one. If all the above examination shows normal ,then check
whether the terminal plug of the magnetron and the capacitor
have loosened, if it is loosened, pinch it tightly with a pliers.
5
5
.
.
2
2
.
.
5
5
E
E
X
X
A
A
M
M
I
I
N
N
E
E
T
T
H
H
E
E
S
S
T
T
A
A
R
R
T
T
I
I
N
N
G
G
A
A
N
N
D
D
T
T
H
H
E
E
8
8
A
A
F
F
U
U
S
S
E
E
O
O
F
F
T
T
H
H
E
E
M
M
I
I
C
C
R
R
O
O
W
W
A
A
V
V
E
E
O
O
V
V
E
E
N
N
.
.
Pull out the power plug, take off the cabinet, discharge the
capacitor, measure the resistance value of the primary
winding and the secondary winding of the transformer with an
avometer (FIG.5 – 10 and FIG.5 - 9). The resistance value of
the primary winding should be about 2.2 ohms, the secondary
winding should be about 130 ohms. Otherwise, it indicates the
transformer has broken, and should be replaced by a new
one.
Fig.5-4
Fig.5-5
magnetron
Fig.5-8
