Sharp R21JCA - Commercial Microwave Oven, Supplemental Service Manual, Page: 6 / 24

4
R-21JCA
ITEM DESCRIPTION
Power Requirements 120 Volts
14 Amperes
60 Hertz / Single phase, 3 wire grounded
Power Output 1000 watts (IEC 705 Test Procedure)
Operating frequency of 2450MHz
Case Dimensions Width 20-1/2" (520mm)
Height 12-1/8" (309mm)
Depth 16"
(406mm)
Cooking Cavity Dimensions Width 13-7/8" (353mm)
(1.0 Cubic Feet ) Height 8-1/8" (207mm)
Depth 14-5/8" (370mm)
Control Complement Light Up Dial (6 minutes)
No cooking control
Oven Cavity Light Yes
Safety Standard UL Listed FCC Authorized
DHHS Rules, CFR, Title 21, Chapter 1, Subchapter J, NSF Certified
SPECIFICATION
The following is a description of component functions during
oven operation.
OFF CONDITION
Closing the door activates door sensing switch and second-
ary interlock switch. (In this condition, the monitor switch
contacts are opened.)
When oven is plugged in, 120 volts A.C. is supplied to the
control unit (Figure O-1).
COOKING CONDITION
When the Light Up Dial is turned, the following operations
occur:
1. The contacts of relays are closed and components
connected to the relays are turned on as follows.
(For details, refer to Figure O-2)
RELAY CONNECTED COMPONENTS
RY-1 Oven lamp/ Antenna motor/ Fan motor
RY-2 Power transformer
2. 120 volts A.C. is supplied to the primary winding of the
power transformer and is converted to about 3.2 volts
A.C. output on the filament winding, and approximately
2150 volts A.C. on the high voltage winding.
3. The filament winding voltage heats the magnetron
filament and the H.V. winding voltage is sent to a voltage
doubler circuit.
OPERATION
DESCRIPTION OF OPERATING SEQUENCE
4. The microwave energy produced by the magnetron is
channelled through the waveguide into the cavity feed-
box, and then into the cavity where the food is placed to
be cooked.
5. Upon completion of the cooking time, the power
transformer, oven lamp, etc. are turned off, and the
generation of microwave energy is stopped. The oven
will revert to the OFF condition.
6. When the door is opened during a cook cycle, monitor
switch, door sensing switch, secondary interlock switch,
relay (RY2) and primary interlock relay(RY1) are activated
with the following results. The circuits to the antenna
motor, the cooling fan motor, the oven lamp and the high
voltage components are de-energized, and the cooking
program will be canceled when the door was opened.
7. The monitor switch electrically monitors the operation of
the secondary interlock switch and primary interlock
relay(RY1) and is mechanically associated with the door
so that it will function in the following sequence.
(1) When the door opens from the closed position, the primary
interlock relay(RY1) and secondary interlock switch open
their contacts. Then the monitor switch contacts close.
(2) When the door is closed from the open position, the
monitor switch contacts open first. Then the contacts of the
secondary interlock switch and door sensing switch close.
If the secondary interlock switch and primary interlock relay (RY1)
fail with the contacts closed when the door is opened, the closing
of the monitor switch contacts will form a short circuit through the
monitor fuse, secondary interlock switch, and primary interlock
relay(RY1), causing the monitor fuse to blow.