Sharp R-950A Service Manual page 21

R-950A
PROCEDURE
LETTER
rectifier, high voltage wire or filament winding of the power 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.
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 10MΩ 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 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.
E SWITCH TEST
CARRY OUT 3D CHECKS.
Isolate the switch to be tested and using an ohmmeter check between the terminals as described in the
following table.
If incorrect readings are obtained, make the necessary switch adjustment or replace the switch.
CARRY OUT 4R CHECKS.
F BLOWN FUSE M10A
CARRY OUT 3D CHECKS.
1. If the fuse M10A is blown, there could be shorts or grounds in electrical parts or wire harness.
Check them and replace the defective parts or repair the wire harness.
2. If the fuse M10A is blown when the door is opened, check the 1st. latch switch, 2nd interlock relay
control switch, 2nd interlock relay, monitor switch and monitor resistor.
If the fuse M10A is blown by incorrect door switching, replace the defective switch(es) and the fuse
M10A.
3. If the fuse M10A is blown, there could be 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, power transformer or H.V. wire. Check them and replace the defective parts
or repair the wire harness.
CARRY OUT 4R CHECKS.
CAUTION: Only replace fuse M10A with the correct value replacement.
G FUSE 20A
CARRY OUT 3D CHECKS.
If the fuse 20A is blown, there is a shorts or grounds in electrical parts or wire harness. Check them
and replace the defective parts or repair the wire harness.
CARRY OUT 4R CHECKS.
CAUTION: Only replace fuse 20A with the correct value replacement.
TEST PROCEDURES
Table: Terminal Connection of Switch
Plunger Operation COM to NO
Released Open Circuit
Short Circuit
Depressed
COMPONENT TEST
COM to NC
Short Circuit
Open Circuit
14
COM; Common terminal
NO; Normally open terminal
NC; Normally close terminal