R1900J
6 – 6
[16] P: CONTROL UNIT TEST
The following symptoms indicate a defective control unit. Before replacing the control unit, perform the Key units test (Procedure O) to determine if
control unit is faulty.
Connect the power supply cord. And check for followings.
1. In connection with pads.
1) When touching the pads, a certain group of pads do not produce a signal.
2) When touching the pads, no pads produce a signal.
2. In connection with display
1) At a certain digit, all or some segments do not light up.
2) At a certain digit, brightness is low.
3) Only one indicator does not light.
4) The corresponding segments of all digits do not light up; or they continue to light up.
5) Wrong figure appears.
6) A certain group of indicators do not light up.
7) The figure of all digits flicker.
3. Other possible problems caused by defective control unit.
1) Buzzer does not sound or continues to sound.
2) Cooking is not possible.
4. If the protectors F1 and/or F2 on the control unit PWB are open, the control unit is defective. To check, carry out following procedures.
i)
Disconnect the power supply cord, and then remove outer case and rear cover.
ii) Open the door and block it open.
iii) Discharge two high voltage capacitors.
iv) Remove the control unit from the control panel, referring to “CONTROL PANEL ASSEMBLY AND CONTROL UNIT REMOVAL”.
v) Check the continuity of the protectors F1 and F2 on the control unit
[17] Q: POWER UNIT TEST
1. Check the out put voltage of power unit at CN21 as follows.
i)
Disconnect the power supply cord, and then remove outer case and rear cover.
ii) Open the door and block it open.
iii) Discharge two high voltage capacitors.
iv) Disconnect the leads to the primary of the power transformer.
v) Ensure that these leads remain isolated from other components and oven chassis by using insulation tape.
vi) Check the voltage between Pin No1 and No2 of CN21.
vii) The output voltage should be approx. 24V.
viii) If not so, the power unit is defective.
2. Check the continuity of the fuse F1 and protector F21 on the power unit as follows.
i)
Disconnect the power supply cord, and then remove outer case and rear cover.
ii) Open the door and block it open.
iii) Discharge two high voltage capacitors.
iv) Remove the power unit from the oven, referring to “POWER UNIT REMOVAL”.
v) Check the continuity of the fuse F1 and the protector F21.
vi) If they are open, the power unit is defective
[18] R: RELAY UNIT TEST
1. CARRY OUT
3D
CHECKS.
2. Remove the relay unit from the oven, referring to “RELAY UNIT REMOVAL”.
3. Check the continuity of the FUSE1 on the relay unit.
1) If it is open, the relay unit is defective.
4. Check the open and /or short of the transformer primary coil on the relay unit.
1) If it is open and /or short, it is defective.
5. Check the state of the relays contacts RY-1, RY-2 and RY-3 using an ohmmeter.
1) The relay contacts should be open. If not so, the relay unit is defective.
