Read Sharp R-1900M (serv.man7) Service Manual online
R1900M
6 – 5
3. CARRY OUT 4R CHECKS.
CAUTION: IF THE TEMPERATURE FUSE INDICATES AN OPEN CIRCUIT AT ROOM TEMPERATURE, REPLACE TEMPERATURE FUSE.
[12] L: MAGNETRON THERMISTOR TEST
1. CARRY OUT 3D CHECKS.
2. Disconnect the connector of the magnetron thermistor from the harness. Measure the resistance of the thermistor with an ohmmeter. Connect the
ohmmeter leads to the connector of the thermistor.
If the meter does not indicate above resistance, replace the thermistor.
3. CARRY OUT 4R CHECKS.
[13] M: EXHAUST THERMISTOR TEST
The exhaust thermistor can be checked by using the Special function (SF-6). Check the exhaust thermistor, referring to the pages of the Exhaust ther-
mistor check (SF-6).
mistor check (SF-6).
If the display shows “OH”, the exhaust thermistor is normal. If the display shows “no”, the exhaust thermistor is abnormal and it should be replaced.
[14] N: NOISE FILTER TEST
1. CARRY OUT 3D CHECKS.
2. Disconnect the lead wires from the terminal the noise filter. Using an ohmmeter, check
between the terminals as described in the following table. If incorrect reading are obtained,
replace the noise filter.
replace the noise filter.
3. CARRY OUT 4R CHECKS.
[15] O: KEY UNIT TEST
1. CARRY OUT 3D CHECKS.
2. Check Key unit ribbon connection before replacement.
3. If key unit ribbon connection is normal, carry out the following procedures.
4. Re-install the rear cover and the outer case (cabinet).
5. Reconnect the power supply cord.
6. The following symptoms indicate a defective key unit.
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.
7. When you can not judge if the key unit is normal or not by using the item 8 above, carry out following test procedures.
1) Disconnect the power supply cord, and then remove outer case and rear cover.
2) Open the door and block it open.
3) Discharge two high voltage capacitors.
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.
6) Reconnect the power supply cord.
Room temperature
Resistance
20
°C
Approx. 750K
Ω
MEASURING POINT
INDICATION OF OHMMETER
Between source terminals
Approx. 470K
Ω
Between source (Black) and load (Black) terminals
Short circuit.
Between source (White) and load (White/Brown) terminals
Short circuit.
WEAK
POINT
NOISE FILTER
NOISE SUPPRESSION COIL
LINE CROSS CAPACITOR
1.0μF / AC 275V
DISCHARGE RESISTOR
470K 1/2W
LINE BYPASS
CAPACITOR
0.0033μF / AC 250V
LINE BYPASS
CAPACITOR
0.0033μF / AC 250V
Load
(Black)
Load
(Gray/White)
Source
(Blue)
Source
(Brown)
5
4
3
2
7
8
9
6
1
2
3
4
3
4
1
5
6
7
2
3
4
3
4
1
5
6
7
2
3
4
3
4
1
5
6
7
8
8
STOP
CLEAR
1
START
3
4
9
5
6
0
7
8
STOP
CLEAR
1
2
X2/X3
START
3
4
9
5
6
0
7
8
CN-M
CN-R
CN-Z
2
CUSTOM
SETTING
SET
MEMORY
EXPRESS
DEFROST
MANUAL
REHEAT
POWER
LEVEL
CN-Q
< DOOR KEY UNIT >
< KEY UNIT >
< SW UNIT >
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