R-7N76(W)M
R-7N76(B)M
13
TEST PROCEDURES (CONT'D)
PROCEDURE
LETTER
COMPONENT TEST
Initial temperature .................................................................................................. T1 = 11
°
C
Temperature after (49 + 3) = 52 sec. ..................................................................... T2 = 21
°
C
Temperature difference Cold-Warm ....................................................................
∆
T1 = 10
°
C
Measured output power
The equation is “P = 85 x
∆
T” ...................................................... P = 85 x 10
°
C = 850 Watts
JUDGMENT: The measured output power should be at least
±
15 % of the rated output power.
CAUTION:1
°
C CORRESPONDS TO 85 WATTS. REPEAT MEASUREMENT IF THE POWER IS
INSUFFICIENT.
1000g
1000g
1000g
T1˚C
T2˚C
Heat up for 52 sec.
B
HIGH VOLTAGE TRANSFORMER TEST
WARNING: High voltages and large currents are present at the secondary winding and
filament winding 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:-
If the reading obtained are not stated above, then the high voltage transformer is probably faulty and
should be replaced.
CARRY OUT 4R CHECKS
C
HIGH VOLTAGE RECTIFIER ASSEMBLY TEST
a. Primary winding
1.55 ohms approximately
b. Secondary winding
85 ohms approximately
c. Filament winding
less than 1 ohm
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.
CARRY OUT 4R CHECKS
ASYMMETRIC RECTIFIER TEST
A
B
C
D2
D1
ASYMMETRIC
RECTIFIER
HIGH VOLTAGE RECTIFIER
CARRY OUT 3D CHECKS.
