R-234 (serv.man2). Part 1 Text (1-28) - Sharp Home Appliance Service Manual (repair manual). Page 14

R-234 - 14

CARRY OUT 3D CHECKS

Isolate the switch to be tested and using an ohmmeter check between the terminals as described in the
following table.

COM;

Common terminal

NO;

Normally open terminal

NC;

Normally close terminal

Table: Terminal Connection of Switch

Plunger Operation

COM to NO

COM to NC

Released

Open circuit

Short circuit

Depressed

Short circuit

Open Circuit

If incorrect readings are obtained, make the necessary switch adjustment or replace the switch.

CARRY OUT 4R CHECKS.

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 10 M

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 10 M

Ω

resistance.

F. When the internal wire is opened in the high voltage capacitor, the 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

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 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.

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.