Sharp R-8470, Service Manual

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R-8470
-8570
The relay unit consists of circuits including the shut-off relays, buzzer, transformer, etc.
Plug power cord into wall receptacle “88888” will be flashing in the display.
Remove the outer case and check voltage between Pin Nos.
1 and 3 of the connector
(A) on the relay unit with an A.C. voltmeter.
The meter should indicate 240 volts, if not check oven circuit.
Shut-off , Cook and Heater Relay Test These relays are operated by D.C. voltage.
Check voltage at the relay coil with a D.C. voltmeter during the microwave or convection cooking
operation.
DC. voltage indicated
. . . . . . . . . . Defective relay.
DC. voltage not indicated . . . . . . ..Check diode which is connected to the relay coil. If diode is
good, control unit is defective.
RELAY SYMBOL
( C O O K )
RY2
RY3
RY4 (HEATER)
RY5
RY6
OPERATIONAL
VOLTAGE
Approx. 14 V.D.C.
Approx. 14 V.D.C.
Approx. 14 V.D.C.
Approx. 14 V.D.C.
Approx. 14 V.D.C.
Approx. 14 V.D.C.
CONNECTED COMPONENTS
Power transformer
Oven lamp/Turntable motor
Convection motor
Heating element
Cooling fan motor
Damper motor
The touch control panel consists of circuits including semiconductors such as LSI,
Therefore, unlike conventional microwave ovens, proper maintenance cannot be performed with
only a voltmeter and ohmmeter. In this service manual, the touch control panel assembly is di-
vided into three units Control Unit, Key Unit and Relay Unit and troubleshooting by unit re-
placement is described according to the symptoms indicated.
1. Key Unit.
The following symptoms indicate a defective key unit. Replace the key un it.
a) When touching the pads, a certain pad produces no signal at all.
b) When touching a number pad, two figures or more are displayed.
c) When touching the pads, sometimes a pad produces no signal.
2. Control Unit
The following symptoms indicate a defective control unit. Replace the control unit.
2-l In connection with pads.
a) When touching the pads, a certain group of pads do not produce a signal.
b) When touching the pads, no pads produce
2-2 In connection with indicators
a) At a certain digit, all or some segments do not light up.
b) At a certain digit, brightness is low when it lights-up.
c) Only one indicator does not light up.
d) The corresponding segments of all digits do not light up; or they continue to light up.
e) Wrong figure appears.
f)
A certain group of indicators do not light up.
g) The figure of all digits flicker.
2-3 Other possible troubles caused by defective control unit.
a)
Buzzer does not sound or continues to sound.
b) Clock does not operate properly.
c) Cooking is not possible.
d) Proper temperature measurement is not obtained.
Note: When a defective one or more of three components, the Control Unit, Key Unit or Relay
Unit are replaced, the defective part or parts must be properly packed for return in the
shipping carton, with its cushion material, in which the new replacement part was shipped
to you.