Sharp R-22AM Service Manual page 15

PROCEDURE
LETTER
Room temperature ................................................................................................. T0 = 21°C
Initial temperature .................................................................................................. T1 = 11°C
Temperature after (28 + 3) = 31 sec [for R-22AM] ................................................. T2 = 21°C
Temperature after (23 + 3) = 26 sec [for R-23AM/23AT] ....................................... T2 = 21°C
Temperature difference Cold-Warm ...................................................................... ∆T1 = 10˚C
Measured output power
The equation is "P = 150 x ∆T" [for R-22AM] .......................... P = 150 x 10°C = 1500 Watts
The equation is "P = 180 x ∆T" [for R-23AM/23AT] ................ P = 180 x 10°C = 1800 Watts
JUDGMENT: The measured output power should be within the range of
CAUTION: 1°C CORRESPONDS TO 150 WATTS [R-22AM]/ 180 WATTS [R-23AM, R-23AT]. REPEAT
B HIGH VOLTAGE TRANSFORMER TEST
WARNING:
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:-
If the readings obtained are not stated as above, then the high voltage transformer is probably faulty
and should be replaced.
CARRY OUT 4R CHECKS.
C HIGH VOLTAGE RECTIFIER ASSEMBLY 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 infinite in one direction and more than 100 kΩ in the other direction.
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.
TEST PROCEDURES
power.
MEASUREMENT IF THE POWER IS INSUFFICIENT.
1000g
1000g
T1˚C
Heat up for 31 sec. for R-22AM
Heat up for 26 sec. for R-23AM/ R-23AT
High voltage and large currents are present at the secondary winding and
filament winding of the 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.
a. Primary winding
b. Secondary winding
c. Filament winding
COMPONENT TEST
R-22AM
approximately 1.8 Ω
approximately 75 Ω
less than 1 Ω
B
13
±
15 % of the rated output
1000g
T2˚C
R-23AM, R-23AT
approximately 1.2 Ω
approximately 75 Ω
C
HIGH VOLTAGE RECTIFIER
R-22AM
R-23AM
R - 2 3 A T