Bosch HMB402, Service Manual

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5-14
CONDITION CHECK RESULT CAUSE REMEDY
1. Setting time
does not count
down when
touching START
pad.
2. Fan motor or
oven lamp do
not turn on.
No continuity.
Continuity.
Continuity
Defective PCB
assembly.
Loose connection.
Replace PCB
assembly.
Connect them
tightly.
No continuity
Abnormal Check fan motor. Defective fan motor. Replace fan motor.
Abnormal
Normal
Check oven lamp.
Defective oven lamp. Replace oven lamp.
Defective
secondary switch. Replace
secondary switch.
Check continuity
of secondary
switch (with
door closed).
Check the con-
nection between
CN1 connector
and PCB
assembly.
(TROUBLE 3) Display shows all figures set, but oven does not start cooking while desired
program times are set and START pad is touched.
(TROUBLE 4) Oven seems to be operating but little heat is produced in oven load.
NOTE : Simple test of power output-conducted by heating one liter water for one min. if available.
Minimum 8.5°C temperature rise is normal condition.
CONDITION CHECK RESULT CAUSE REMEDY
Output is low
Lower than 90% of
rating voltage.
Normal
Abnormal
Defective PCB
assembly. Replace PCB
assembly.
Normal
Abnormal
Measure the
output power. Defective
magnetron. Replace
magnetron.
Decrease in power
source voltage
with load. Suggest customer
contact local
electric power
utility co. or
qualified
electrician.
Check the
power source
voltage.
Disconnect the
wire leads from
relay 2 and
check on and off
time with
multitester.