Read Sharp R-27STMA (serv.man6) Service Manual online
R27STMA
6 – 1
R27STMA
Service Manual
CHAPTER 6.
FUNCTION OF IMPORTANT COMPONENTS
[1] DOOR OPEN MECHANISM
The door is opened by pulling the door, refer to the Figure D-1.
Figure D-1. Door Open Mechanism
[2] SECONDARY INTERLOCK SWITCH
1. When the oven door is closed, the contacts (COM-NO) of the
switch must be closed. And the contacts (COMNC) must be
opened.
opened.
2. When the oven door is opened, the contacts (COMNO) of the
switch must be opened. And the contacts (COM-NC) must be
closed.
closed.
[3] DOOR SENSING 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.
[4] 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 sec-
ondary interlock switch and the primary interlock relay (RY2) fail to
open, the fuse T6.3A blows simultaneously with closing the con-
tacts (COM-NC) of the monitor switch.
open, the fuse T6.3A blows simultaneously with closing the con-
tacts (COM-NC) of the monitor switch.
CAUTION: BEFORE REPLACING A FUSE T6.3A TEST THE SEC-
ONDARY INTERLOCK SWITCH AND PRIMARY INTER-
LOCK RELAY (RY2) AND MONITOR SWITCH FOR
PROPER OPERATION. (REFER TO CHAPTER “TEST
PROCEDURE”.)
LOCK RELAY (RY2) AND MONITOR SWITCH FOR
PROPER OPERATION. (REFER TO CHAPTER “TEST
PROCEDURE”.)
[5] FUSE T6.3A
1. The fuse T6.3A blows when the contacts (COM-NO) of the second-
ary interlock switch and the primary interlock relay (RY2) remain
closed with the oven door open and when the monitor switch
closes.
closed with the oven door open and when the monitor switch
closes.
2. If the wire harness or electrical components are short-circuited, the
fuse T6.3A blows to prevent an electric shock of fire hazard.
[6] TEMPERATURE FUSE 150C (OVEN)
The temperature fuse ocated 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 temperature fuse remains
closed. However, when abnormally high temperatures are reached
within the oven cavity, the temperature fuse will open at 150
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 temperature fuse remains
closed. However, when abnormally high temperatures are reached
within the oven cavity, the temperature fuse will open at 150
°C, caus-
ing the oven to shut down. The defective temperature fuse must be
replaced with a new one.
replaced with a new one.
[7] ASYMMETRIC RECTIFIER
The asymmetric rectifier is solid state device that prevents current flow
in both directions. And it prevents the temperature rise of the high volt-
age transformer by blowing the fuse T6.3A when the high voltage rec-
tifier is shorted.
in both directions. And it prevents the temperature rise of the high volt-
age transformer by blowing the fuse T6.3A when the high voltage rec-
tifier is shorted.
The rated peak reverse voltage of D1 of the asymmetric rectifier is 6
KV The rated peak reverse voltage of D2 of the asymmetric rectifier is
1.7 KV. D1 and D2 of the asymmetric rectifier or high voltage rectifier
are shorted when the each peak reverse voltage goes beyond the
each rated peak reverse voltage. (The process of the blowing the fuse
T6.3A.)
KV The rated peak reverse voltage of D2 of the asymmetric rectifier is
1.7 KV. D1 and D2 of the asymmetric rectifier or high voltage rectifier
are shorted when the each peak reverse voltage goes beyond the
each rated peak reverse voltage. (The process of the blowing the fuse
T6.3A.)
1. The high voltage rectifier is shorted by some fault when microwave
cooking or dual cooking.
2. The peak reverse voltage of D2 of the rectifier goes beyond the
rated peak reverse voltage 1.7 KV in the voltage doubler circuit.
3. D2 of the rectifier is shorted.
4. The large electric currents flow through the high voltage winding of
the high voltage transformer.
5. The large electric currents beyond 6.3A flow through the primary
winding of the high voltage transformer.
6. The fuse T6.3A blows by the large electric currents.
7. The power supplying to the high voltage transformer is cut off.
[8] TURNTABLE MOTOR
The turntable motor drives the turntable roller assembly to rotate the
turntable.
turntable.
[9] 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 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.
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.
[10] NOISE FILTER
The noise filter prevents the radio frequency interference that might
flow back in the power circuit.
flow back in the power circuit.
Latch Heads
Latch Hook
Door
Door Sensing Switch
Secondary interlock Switch
Monitor Switch
D2
D1
ASYMMETRIC
RECTIFIER
HIGH VOLTAGE
RECTIFIER
Display
