Troubleshooting Guide - Sharp R-203CW Service Manual

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R-203CW

blowing the C/T fuse, when the contacts of the primary

interlock relay (RY2) and secondary interlock switch fail to

open when the door is opened.

Functions:

1. When the door is opened, the monitor switch contacts

close (to the ON condition) due to their being normally

closed. At this time the primary interlock relay (RY2) and

secondary interlock switch are in the OFF condition

(contacts open) due to its being normally open contact

switches.

2. As the door goes to a closed position, the monitor switch

contacts are first opened and then the door sensing

switch and secondary interlock switch contacts close.

3. If the door is opened, and the primary interlock relay

(RY2) and the secondary interlock switch contact fail to

open, the C/T fuse blows simultaneously with closing of

the monitor switch contacts.

CAUTION: BEFORE REPLACING A BLOWN C/T FUSE,

TEST THE DOOR SENSING SWITCH, PRI-

MARY INTERLOCK RELAY (RY2), SECOND-

ARY INTERLOCK SWITCH AND MONITOR

SWITCH FOR PROPER OPERATION. (RE-

FER TO CHAPTER "TEST PROCEDURE").

NOTE: C/T FUSE AND MONITOR SWITCH ARE

REPLACED AS AN ASSEMBLY

TURNTABLE MOTOR

The turntable motor rotates the turntable located on the

bottom of the oven cavity, so that the food on the turntable

is cooked evenly. The turntable may turn in either direction.

COOLING FAN MOTOR

The cooling fan motor drives a blade which draws external

Never touch any part in the circuit with your hand or an uninsulated tool while the power supply is connected.

When troubleshooting the microwave oven, it is helpful to follow the Sequence of Operation in performing the checks. Many

of the possible causes of trouble will require that a specific test be performed. These tests are given a procedure letter which

will be found in the "Test Procedure "section.

IMPORTANT: If the oven becomes inoperative because of a blown C/T fuse, check the monitor switch, primary

interlock relay (RY2), door sensing switch and secondary interlock switch before replacing the C/T fuse.

If the C/T fuse is replaced, the monitor switch must also be replaced. Use part FFS-BA020WRK0 as an

assembly.

IMPORTANT: Whenever troubleshooting is performed with the power supply cord disconnected. It may in, some cases,

be necessary to connect the power supply cord after the outer case has been removed, in this event,

1. Disconnect the power supply cord, and then remove outer case.

2. Open the door and block it open.

3. Discharge high voltage capacitor.

cool air. This cool air is directed through the air vanes

surrounding the magnetron and cools the magnetron. This

air is channelled through the oven cavity to remove steam

and vapours given off from the heating foods. It is then

exhausted through the exhausting air vents at the oven

cavity.

MAGNETRON THERMAL CUT-OUT

The thermal cut-out located on the top of the oven cavity is

designed to prevent damage to the magnetron if an over

heated condition develops in the tube due to cooling fan

failure, obstructed air guide, dirty or blocked air intake, etc.

Under normal operation, the thermal cut-out remains closed.

However, when abnormally high temperatures are reached

within the magnetron, the thermal cut-out will open at 257˚F

(125˚C), causing the oven to shut down.

C/T FUSE

1. The C/T fuse blows when the contacts (COM-NO) of the

2. If the wire harness or electrical components are short-

3. The C/T fuse, located on the top of the oven cavity, is

Under normal operation, the C/T fuse remains closed.

However, when abnormally high temperatures are reached

within the oven cavity, the C/T fuse will open at 248˚F

(120˚C), causing the oven to shut down or when the electric

currents beyond 13A flow, the C/T fuse will open.