Microwave Oven User Manual

11
MMD24S
MMD24B
TEST PROCEDURES
PROCEDURE
LETTER
COMPONENT TEST
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,
Keyboard Unit and Power Unit, and troubleshooting by unit replacement is described according to the
symptoms indicated.
Before testing,
1) Disconnect the power supply cord, and then disassemble as per "MICROWAVE DRAWER
DISASSEMBLY" page 27.
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
insulation tape.
1. Keyboard Unit.
NOTE ;
1) Check Keyboard unit connection before replacement.
2) Reconnect all leads removed from components during testing.
3) Re-install the covers.
4) Reconnect the power supply cord after the covers are installed.
5) Run the oven and check all functions.
The following symptoms indicate a defective keyboard unit.
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.
1) Disconnect the power supply cord, and then remove covers.
2) Open the drawer 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 covers are 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 B) to determine if control unit is faulty.
2-1 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.
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.
2-2 Other possible problems 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.
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,
1) Disconnect the power supply cord, and then disassemble as per "MICROWAVE DRAWER
DISASSEMBLY" page 27.
2) Open the drawer and block it open.
3) Discharge high voltage capacitor.
A TOUCH CONTROL PANEL ASSEMBLY TEST
The touch control panel consists of circuits including semiconductors such as LSI, ICs, etc. Therefore,