J: Touch Control Panel Assembly Test; K: Switch Unit Test; L: Relay (Ry1, Ry2) Test - Sharp R-26ST-A Service Manual

Operation manual (182 pages)

Table of Contents

R26STA

[10] J: TOUCH CONTROL PANEL ASSEMBLY TEST

The touch control panel consists of circuits including semiconductors such as LSI, ICs, etc. 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 divided into two

units, Control Unit and Switch Unit, and also the Control Unit is divided into two units, CPU Unit and Power Unit, and troubleshooting by unit replace-

ment is described according to the symptoms indicated.

1. Switch Unit. Note: Check switch unit wire harness connection before replacement.

The following symptoms indicate a defective switch unit. Replace the switch unit.

1) When touching the buttons, a certain button produces no signal at all.

2) When touching the buttons, sometimes a button produces no signal.

3) When rotating the TIMER/WEIGHT knob, the cooking time or the weight can not be input.

2. Control Unit.

The following symptoms indicate a defective control unit. Before replacing the switch unit, perform the Switch unit test (Procedure L) to determine

if control unit is faulty.

1) In connection with buttons.

a) When touching the buttons, a certain group of buttons do not produce a signal.

b) When touching the buttons, no buttons produce a signal.

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.

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.

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.

[11] K: SWITCH UNIT TEST

1. CARRY OUT 3D CHECKS.

2. Isolate the switch unit with the control panel frame to be tested.

3. Using an ohmmeter and referring to the switch unit matrix indicated on the switch unit circuit, check the circuit between the pins of the switch unit

that correspond to the STOP button. When the button is pressed, the ohmmeter should indicate short circuit. When the button is released, the

ohmmeter should indicate open circuit. If incorrect readings are obtained, the switch unitbutton is faulty and must be replaced. About the other but-

tons, the above method may be used.

4. CARRY OUT 4R CHECKS.

[12] L: RELAY (RY2, RY5, RY6) TEST

CARRY OUT 3D CHECKS.

Remove the outer case and check voltage between the pin No. 3 and No. 5 of connector CN-A on the control unit with an A.C. voltmeter. The meter

should indicate 230 volts, if not check oven circuit.

Relay Test

These relays are operated by D.C. voltage

C SW100

(G10)