12
R-2275
R-2285
PROCEDURE
LETTER
COMPONENT TEST
TEST PROCEDURES (CONT'D)
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.
Isolate the switch to be tested and using an ohmmeter check between the terminals as described in the
following table.
Table: Terminal Connection of Switch
Plunger Operation
COM to NO
COM to NC
Released
O.C.
S.C.
Depressed
S.C.
O.C.
COM; Common terminal, NO; Normally open terminal NC; Normally close terminal
S.C.; Short, O.C.; Open circuit
CARRY OUT 3D CHECKS
E
SWITCH TEST
D
HIGH VOLTAGE CAPACITOR TEST
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
If incorrect readings are obtained, make the necessary switch adjustment or replace the switch.
CARRY OUT 4R CHECKS.
F
WEAK POINT / FUSE (WP1 OR WP2) TEST
CARRY OUT 3D CHECKS.
If the weak point / fuse WP1 or WP2 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 occurred 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
CAUTION: Only replace weak point /fuse with the correct value replacement.
