Sharp r-3a88 ユーザーズマニュアル

10

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.

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.

CARRY OUT 3D CHECKS.

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

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

CARRY OUT 4R CHECKS.

 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 table below.

 CARRY OUT 4R CHECKS

.Table:  Thermal cut-out Test

Temperature of "ON" condition

Temperature of  "OFF" condition

Indication ofohmmeter

Parts Name

(closed circuit) (˚C)

(open circuit) (˚C)

(When room temperature
 is approx. 20˚C)

Thermal cut-out  145˚C

This is not resetable type

Above 145˚C

Closed circuit.

Thermal cut-out 95˚C

Below 75˚C

Above 95˚C

Closed circuit.

 If incorrect readings are obtained, replace the thermal cut-out.

An open circuit thermal cut-out 145˚C (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 145˚C (OVEN) indicates that the foods in the oven may catch fire, this
may  be due to over heating produced by improper setting of the cooking time or failure of the control
panel.

 An open circuit thermal cut-out 95˚C (FAN) indicates that the fan motor winding has overheated, this
may be due to blocked ventilation or locked cooling fan.