Sharp R-450H, Service Manual

R-450H

5

Figure D-1. Door Open Mechanism

1ST. LATCH SWITCH AND 2ND. INTERLOCK RE-
LAY CONTROL SWITCH

1. When the oven door is closed, the contacts (COM-NO)

must be closed.

2. When the oven door is opened, the contacts (COM-

NO) must be opened.

MONITOR SWITCH

1. When the oven door is closed, the contacts (COM-NC)

must be opened.

2. When the oven door is opened, the contacts (COM-

NC) must be closed.

3. If the oven door is opened and the contacts (COM-NO)

of the 1st. latch switch and 2nd. interlock relay fail to
open, the fuse (F10A) blows  simultaneously with
closing the contacts (COM-NC) of the monitor switch.

CAUTION: BEFORE REPLACING A BLOWN FUSE

(F10A) TEST THE 1ST. LATCH SWITCH,
2ND. INTERLOCK RELAY AND MONITOR
SWITCH FOR PROPER OPERATION. (RE-
FER TO CHAPTER "TEST PROCEDURE".)

FUSE (F10A)

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

circuited, this fuse blows to prevent an electric shock or
fire hazard.

2. The fuse also blows when 1st. latch switch and 2nd.

interlock relay remains closed with the oven door open
and when the monitor switch closes.

HIGH VOLTAGE FUSE 0.75A

The high voltage fuse blows when the high voltage rectifier
or magnetron is shorted.

FUNCTION OF IMPORTANT COMPONENTS

DOOR OPEN MECHANISM

The door can be opened by pushing the door open button
on the control panel. When the door open button is
pushed, the latch lever is moved upward, operating the
latch head. The latch head is moved upward, and released
from latch hook. Now the door can be opened.

THERMAL CUT-OUT 145˚C (OVEN)

The thermal cut-out located on the top of the oven cavity
is designed to prevent damage to the oven if the foods in
the oven catch fire due to over heating produced by
improper setting of cook time or failure of control unit.
Under normal operation, the oven thermal cut-out remains
closed. However, when abnormally high temperature is
reached within the oven cavity, the oven thermal cut-out
will open at 145˚C, causing the oven to shut down. The
defective thermal cut-out must be replaced with new one.

THERMAL CUT-OUT 145˚C (MAGNETRON)

The thermal cut-out located near the magnetron is de-
signed 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 145˚C causing the oven to shut down. The
defective thermal cut-out must be replaced with new one.

TURNTABLE MOTOR

The turntable motor drives the turntable roller assembly to
rotate the turntable.

FAN MOTOR

The fan motor drives a blade which draws external cool air.
This cool air is directed through the air vanes surrounding
the magnetron and cools the magnetron. This air is chan-
nelled through the oven cavity to remove steam and
vapours given off from the heating foods. It is then ex-
hausted through the exhausting air vents at the oven
cavity.

NOISE FILTER

The noise filter prevents the radio frequency interference
that might flow back in the power circuit.

Latch Hook

1st. Latch
Switch

Monitor 
Switch

Switch
Lever

Latch
Heads

Door

2nd. Interlock
Relay Control 
Switch