Sharp R-2397, Service Manual

Page: 13 / 44

11
R-2397
TEST PROCEDURES
PROCEDURE
LETTER
COMPONENT TEST
Initial temperature ............................................................................................... T1 = 11
°
C
Temperature after (25 + 3) = 28 sec. . ................................................................ T2 = 21
°
C
Temperature difference Cold-Warm ...................................................................
∆
T = 10
°
C
Measured output power
The equation is “P = 170 x
∆
T” .............................................. P = 170 x 10
°
C = 1700 Watts
JUDGMENT: The measured output power should be at least
±
15 % of the rated output power.
CAUTION: 1
°
C CORRESPONDS TO 170 WATTS. REPEAT MEASUREMENT IF THE POWER IS
INSUFFICIENT.
1000g
1000g
1000g
T1˚C
T2˚C
Heat up for 28 sec.
B HIGH VOLTAGE TRANSFORMER TEST
WARNING: High voltages and large currents are present at the secondary winding and
filament winding of high voltage transformer. It is very dangerous to work
near this part when the oven is on. NEVER make any voltage measurements
of the high-voltage circuits, including the magnetron filament.
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
b. Secondary winding approx. 57.3
Ω
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.
A B
C
D2 D1
ASYMMETRIC
RECTIFIER
HIGH VOLTAGE RECTIFIER
C HIGH VOLTAGE RECTIFIER ASSEMBLY TEST
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.