J: High Voltage Fuse Test; K: Touch Control Panel Assembly Test; L: Key Unit (Membrane Switch) Test - Sharp R-380LS Service Manual

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Table of Contents

R380L(W)

[10] J: HIGH VOLTAGE FUSE TEST

CARRY OUT 3D CHECKS.

If the high voltage fuse is blown, there could be a short in the high voltage rectifier or the magnetron.

Check them and replace the defective parts and the high voltage fuse.

CARRY OUT 4R CHECKS.

CAUTION: ONLY REPLACE HIGH VOLTAGE FUSE WITH THE CORRECT VALUE REPLACEMENT.

[11] K: 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 Key Unit, and also the Control Unit is divided into two units, CPU Unit and Power Unit, and troubleshooting by unit replacement

is described according to the symptoms indicated.

1. Key Unit. Note: Check key unit ribbon connection before replacement.

The following symptoms indicate a defective key unit. Replace the control unit assembly.

1) When touching the pads, a certain pad produces no signal at all.

2) When touching a number pad, two figures or more are displayed.

3) When touching the pads, sometimes a pad produces no signal.

2. Control Unit.

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

control unit is faulty.

1) 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 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.

[12] L: KEY UNIT (MEMBRANE SWITCH) TEST

If the display fails to clear when the STOP/CLEAR pad is depressed, first verify the flat ribbon cable is making good contact, verify that the 2nd. inter-

lock relay control switch operates properly; that is the contacts are closed when the door is closed and open when the door is open. If the 2nd. inter-

lock relay control switch is good, disconnect the flat ribbon cable that connects the key unit to the control unit and make sure the 2nd. interlock relay

control switch is closed (either close the door or short the 2nd. interlock relay control switch connector). Use the key unit matrix indicated on the con-

trol panel schematic and place a jumper wire between the pins that correspond to the STOP/CLEAR pad making momentary contact.If the control unit

responds by clearing with a beep the key unit is faulty and must be replaced. If the control unit does not respond, it is faulty and must be replaced. If

a specific pad does not respond, the above method may be used (after clearing the control unit) to determine if the control unit or keypad is at fault.

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