Sharp R-4P58 - Page 16

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PROCEDURE
LETTER
TEST PROCEDURES (CONT'D)
COMPONENT TEST
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, BE-
CAUSE OTHERWISE AN INFINITE RESISTANCE MIGHT BE SHOWN IN BOTH DIREC-
TIONS.
HIGH VOLTAGE CAPACITOR TEST
CARRY OUT 3D CHECKS.
. Isolate the high voltage capacitor from the circuit.
. Continuity check must be carried out with measuring instrument which is set to the highest
resistance range.
. Anormal capacitor shows continuity for a short time (kick) and then a resistance of about 10MQ
after it has been charged.
. A short-circuited capacitor shows continuity all the time.
. An open capacitor constantly shows a resistance about 10 MQ because of its internal 1OMQ
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.
GARRY OUT 4R CHECKS.
SWITCH TEST
CARRY OUT 8D CHECKS.
Isolate the switch to be tested and using an ohmmeter check between the terminals as described in
the following table.
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Table: Terminal Connection of Switch
Plunger Operation COM to NO COM to NC COM; Common terminal,
NO; Normally open terminal
NC; Normally close terminal
lf incorrect readings are obtained, make the necessary switch adjustment or replace the switch.
CARRY OUT 4R CHECKS.
THERMAL CUT-OUT TEST
CARRY OUT 3D CHECKS.
Disconnect the leads from the terminals of the thermal cut-out. Then using an ohmmeter, make a continuity
test across the two terminals as described in the below.
Table: Therma] Cut-out Test
Temperature of "ON" Temperature of "OFF" | Indication of ohmmeter
Parts Name condition (closed circuit). | condition (open circuit). | (When roomtemperature
(°C) (°C) is approx. 20°C.)
Thermal cut-out 125°C | Cuts back in at 95°C. Above 125°C Closed circuit
Thermal cut-out 150°C | Cuts back in at 120°C. Above 150°C Closed circuit
An open circuit thermal cut-out TC1 (MG) indicates that the magnetron has overheated, this may be
due to resistricted ventilation, cooling fan failure or a fault condition within the magnetron or HV. circuit.
An open circuit thermal cut-out TC2 (OVEN) indicates that the food in the oven cavity may catch fire,
this may be due to over heating produced by improper setting of the cooking timer or failure of the
control panel.
CARRY OUT 4R GHECKS.
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