Test Procedures; Touch Control Panel Assembly Test - Sharp KB-3425LS Service Manual

KB-3425LS/K/W
KB-4425LS/K/W
PROCEDURE
LETTER
A

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 three units, Control Unit and
Keyboard Unit and Power Unit, and troubleshooting by unit replacement is described according to the
symptoms indicated.
Before testing,
) Disconnect the power supply cord, and then disassemble as per "OVEN/MICROWAVE DRAWER
2) Open the drawer and block it open.
3) Discharge high voltage capacitor.
4) Disconnect the leads to the primary of the power transformer.
5) Ensure that these leads remain isolated from other components and oven chassis by using
. Keyboard Unit.
NOTE ;
) Check Keyboard unit connection before replacement.
2) Reconnect all leads removed from components during testing.
3) Re-install the outer case (cabinet).
4) Reconnect the power supply cord after the outer case is installed.
5) Run the oven and check all functions.
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.
If the Keyboard unit is defective.
) Disconnect the power supply cord, and then remove outer case.
2) Open the door and block it open.
3) Discharge high voltage capacitor.
4) Replace the Keyboard unit.
5) Reconnect all leads removed from components during testing.
6) Re-install the covers.
7) Reconnect the power supply cord after the outer case is installed.
8) Run the oven and check all functions.
2. Control Unit
The following symptoms indicate a defective control unit. Before replacing the control unit, perform
the Keyboard unit test (Procedure J) to determine if control unit is faulty.
2- In connection with indicators
2-2 Other possible problems caused by defective control unit.
3. Power Unit or Touch Control Transformer
a) Fan motor, stirrer motor, oven lamp or electrical parts do not turn on or do not turn off.
b) Digital display on the control unit does not show anything.
When testing is completed,
) Disconnect the power supply cord, and then disassemble as per "OVEN/MICROWAVE DRAWER
2) Open the drawer and block it open.
3) Discharge high voltage capacitor.

TEST PROCEDURES

DISASSEMBLY" page 40.
insulation tape.
The following symptoms indicate a defective keyboard unit.
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.
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.
a) Buzzer does not sound or continues to sound.
b) Clock does not operate properly.
c) Cooking is not possible.
DISASSEMBLY" page 40.
COMPONENT TEST
8