12
R-733 -
6. Measure the final water temperature. (Example: The final temperature T2 = 21
°
C)
7. Calculate the microwave power output P in watts from above formula.
Initial temperature ......................................................................................................... T1 = 11
°
C
Temperature after (47 + 3) = 50 sec. ............................................................................ T2 = 21
°
C
Temperature difference Cold-Warm ............................................................................
∆
T1 = 10
°
C
Measured output power
The equation is “P = 90 x
∆
T” ................................................. P = 90 x 10
°
C = 900 Watts Approx.
JUDGMENT: The measured output power should be within at least
±
15 % of the rated output
power.
CAUTION: 1
°
C CORRESPONDS TO 90 WATTS. REPEAT MEASUREMENT IF THE POWER IS
INSUFFICIENT.
CARRY OUT 3D CHECKS
Disconnect the leads to the primary winding of the power 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 ............ 1.9 ohms approximately
b. Secondary winding ....... 13 ohms approximately
c. Filament winding ........... less than 1 ohm
If the reading obtained are not stated above, then the power transformer is probably faulty and should
be replaced.
CARRY OUT 4R CHECKS
PROCEDURE
LETTER
COMPONENT 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 infinite in one direction and more than 100 k
Ω
in the other direction.
WARNING: High voltages and large currents are present at the secondary winding and
filament winding of the power 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.
B
POWER TRANSFORMER TEST
Heat up for 50 sec.
C
HIGH VOLTAGE RECTIFIER ASSEMBLY TEST
1000g
1000g
1000g
T1˚C
T2˚C
TEST PROCEDURES
