TEST PROCEDURES
PROCEDURE
COMPONENT TEST
LETTER
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.
DHIGH 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 10MΩ after it has been charged.
D.A
E.An open capacitor constantly shows a resistance about 10 MΩ because of its internal 10MΩ 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.
ESWITCH TEST
CARRY OUT 3D CHECK.
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 | COM; Common terminal | |||
|
|
| NO; | Normally open terminal |
Plunger Operation | COM to NO | COM to NC | ||
|
|
| NC; | Normally close terminal |
Released | O.C. | S.C. | ||
|
|
| S.C.; | Short circuit |
Depressed | S.C. | O.C. | ||
|
|
| O.C.; | Open circuit |
|
|
| ||
If incorrect readings are obtained, make the necessary switch adjustment or replace the switch.
CARRY OUT 4R CHECKS.
FWEAK POINT A018
CARRY OUT 3D CHECKS.
If the weak point A018 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 occured 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 A018 with the correct value replacement.
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