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11

Initial temperature ...............................................................................................  T1 = 11

°

C

Temperature after (25 + 3) = 28 sec. (R-2397G). ...............................................  T2 = 21

°

C

Temperature after (35 + 3) = 38 sec. (R-2297G) ................................................. T2 = 21

°

C

Temperature difference Cold-Warm ................................................................... 

∆

T = 10

°

C

Measured output power
The equation is “P = 170 x 

∆

T” (R-2397G) ........................... P = 170 x 10

°

C = 1700 Watts

The equation is “P = 120 x 

∆

T” (R-2297G) ........................... P = 120 x 10

°

C = 1200 Watts

JUDGMENT:

The measured output power should be at least 

±

 15 % of the rated output power.

CAUTION: 1

°

C CORRESPONDS TO 170 WATTS (R-2397G)/ 120 WATTS (R-2297G). REPEAT

MEASUREMENT IF THE POWER IS INSUFFICIENT.

1000g

1000g

1000g

Heat up for 28 sec. (R-2397G)
Heat up for 38 sec. (R-2297G)

CARRY OUT 3D CHECKS.

Disconnect the leads to the primary winding of the high voltage transformer. Disconnect the filament

and secondary winding connections from the rest of the HV circuitry. Using an ohmmeter, set on a
low range,  it is possible to check the continuity of all three windings. The following readings should
be obtained:

a. Primary winding

approx. 1.06 

Ω

 (R-2397G)/ approx. 2 

Ω

 (R-2297G)

b. Secondary winding

approx. 57.3 

Ω

 (R-2397G)/approx. 83 

Ω

 (R-2297G)

c. Filament winding

less than 1 

Ω

If the reading obtained are not stated as above, then the high voltage transformer is probably faulty

and should be replaced.

CARRY OUT 4R CHECKS.

HIGH VOLTAGE RECTIFIER TEST

CARRY OUT 3D CHECKS.
Isolate the high voltage rectifier assembly from the HV circuit. The high voltage rectifier  can be
tested using an ohmmeter set to its highest range. Connect the ohmmeter across the terminal B+C
of the high voltage rectifier and note the reading obtained. Reverse the meter leads and note this
second reading.

The normal resistance is infinity in one direction and more than 100 k

Ω

 in the other direction.

CARRY OUT 4R CHECKS.

ASYMMETRIC RECTIFIER TEST

CARRY OUT 3D CHECKS.

12

Isolate the high voltage rectifier assembly from the HV circuit. The asymmetric rectifier can be tested
using an ohmmeter set to its highest range. Contact the ohmmeter across the terminals A+B of the
asymmetric rectifier and note the reading obtained. Reverse the meter leads and note this second
reading. If an open circuit is indicated in both directions then the asymmetric rectifier is good. If an
asymmetric rectifier is shorted in either direction, then the asymmetric rectifier is probably faulty and
must be replaced with high voltage rectifier. When the asymmetric rectifier is defective, check
whether magnetron, high voltage rectifier, high voltage wire or filament winding of the high voltage
transformer is shorted.

CARRY OUT 4R CHECKS.

NOTE: FOR MEASUREMENT OF THE RESISTANCE OF THE RECTIFIER, THE BATTERIES OF

THE MEASURING INSTRUMENT MUST HAVE A VOLTAGE AT LEAST 6 VOLTS,
BECAUSE OTHERWISE AN INFINITE RESISTANCE MIGHT BE SHOWN IN BOTH
DIRECTIONS.

CARRY OUT 3D CHECK.

SIsolate the switch to be tested and using an ohmmeter check between the terminals as described
in the following table.

Table: Terminal Connection of Switch

COM; Common terminal

Plunger Operation

COM to NO

COM to NC

NO;

Normally open terminal

Released

O.C.

S.C.

NC;

Normally close terminal

Depressed

S.C.

O.C.

S.C.; Short circuit

O.C.;  Open circuit

If incorrect readings are obtained, make the necessary switch adjustment or replace the switch.

CARRY OUT 4R CHECKS.

CARRY OUT 3D CHECKS.

A. Isolate the high voltage capacitor from the circuit.
B. Continuity check must be carried out with measuring instrument which is set to the highest

resistance range.

C. A normal capacitor shows continuity for a short time (kick) and then a resistance of about 10M

Ω

after it has been charged.

D. A short-circuited capacitor shows continuity all the time.
E. An open capacitor constantly shows a resistance about 10 M

Ω

 because of its internal 10M

Ω

resistance.

F. When the internal wire is opened in the high voltage capacitor shows an infinite resistance.
G. The resistance across all the terminals and the chassis must be infinite when the capacitor is

normal.

If incorrect reading are obtained, the high voltage capacitor must be replaced.

CARRY OUT 4R CHECKS.

CARRY OUT 3D CHECKS.

If the fuse M8A (for R-2397G) / M6.3A (for  R-2297G) is blown, there could be a short in the
asymmetric rectifier or there is a ground in wire harness. A short in the asymmetric rectifier may
have occured due to short or ground in H.V. rectifier, magnetron, high voltage transformer or H.V.
wire. Check them and replace the defective parts or repair the wire harness.

CARRY OUT 4R CHECKS.

13

CARRY OUT 3D CHECKS.

If the fuse 13A is blown, there could be a shorts or grounds in electrical parts or wire harness.
Check them and replace the defective parts or repair the wire harness.

CARRY OUT 4R CHECKS.

CARRY OUT 3D CHECKS.

If the fuse F6.3A is blown when the door is opened, check the latch switch, monitor switch and
monitor resistor.
If the fuse F6.3 is blown by incorrect door switching replace the defective switch(s) and the fuse
F6.3A.

CARRY OUT 4R CHECKS.

CARRY OUT 3D CHECKS.

Disconnect the leads from the terminals of the thermal cut-out. Then using an ohmmeter, make a
continuity test across the each two terminals as described in the table below.

CARRY OUT 4R CHECKS.

Table: Thermal Cut-out Test

Temperature of “ON”

Temperature of “OFF”

Indication of ohmmeter

Parts Name

condition (closed circuit).

condition (open circuit).

(When room temperature

(˚C)

(˚C)  is

approx. 20˚C.)

Thermal cut-out 145˚C

This is not resetable type.

Above 145˚C

Closed circuit.

Thermal cut-out 115˚C

This is not resetable type.

Above 115˚C

Closed circuit

If incorrect readings are obtained, replace the thermal cut-out.

An open circuit oven thermal cut-out 115˚C indicates that the oven cavity has over heated, this may
be due to no load operation.

An open circuit magnetron thermal cut-out 145˚C indicates that the magnetron has overheated, this
may be due to resistricted ventilation, cooling fan failure or a fault condition within the magnetron
or HV circuit.

An open circuit blower motor thermal cut-out 115˚C indicates the blower motor winding has
overheated, this may be due to resisted ventilation or locked cooling fan.

CARRY OUT 3D CHECKS.

Disconnect the leads from the monitor resistor. Using an ohmmeter and set on a low range. Check
between the terminals of the monitor resistor.

The resistance of monitor resistor should be read approx. 4.3

Ω

.

If incorrect readings are obtained, replace the monitor resistor.

CARRY OUT 4R CHECKS.

14

CARRY OUT 3D CHECKS.
Disconnect connector-H from the CPU unit. Measure the resistance of the thermistor with an
ohmmeter. Connect the ohmmeter leads to the leads of the thermistor.

Room Temp.

Resistance

15˚C ........................ Approx. 15.91 k

Ω

20˚C ........................ Approx. 13.04 k

Ω

25˚C ........................ Approx. 10.74 k

Ω

If the meter does not indicate above resistance, replace the thermistor.

CARRY OUT 4R CHECKS.

CARRY OUT 3D CHECKS.

Disconnect connector-B from the CPU unit. Measure the resistance of the thermistor with an
ohmmeter. Connect the ohmmeter leads to the leads of the thermistor.

Room Temp.

Resistance

15˚C ........................ Approx. 77.45 k

Ω

20˚C ........................ Approx. 61.47 k

Ω

25˚C ........................ Approx. 49.12 k

Ω

If the meter does not indicate above resistance, replace the thermistor.

CARRY OUT 4R CHECKS.

CARRY OUT 3D CHECKS.

Disconnect connector-D from the CPU unit. Measure the resistance of the thermistor with an
ohmmeter. Connect the ohmmeter leads to the leads of the thermistor.

Room Temp.

Resistance

15˚C ........................ Approx. 15.88 k

Ω

20˚C ........................ Approx. 13.03 k

Ω

25˚C ........................ Approx. 10.74 k

Ω

If the meter does not indicate above resistance, replace the thermistor.

CARRY OUT 4R CHECKS.

CARRY OUT 3D CHECKS.
Disconnect the leads from the motor. Using an ohmmeter, check the resistance between the two
terminals.

Resistance of Blower motor should be approximately 52

Ω

.

Resistance of Stirrer motor should be approximately 8.8 k

Ω

.

If incorrect readings are obtained, replace the motor.

CARRY OUT 4R CHECKS.

CARRY OUT 3D CHECKS.

Disconnect the leads from the terminals of noise filter. Using an ohmmeter, check between the
terminals as described in the following table.