Microwave Oven Hood Combo Service Manual — LIT 4317216
Original 03/97
Page
THEORY OF OPERATION
The microwave oven is powered by the 120- volt line. Whenever the door is closed and a cooking function is programmed through the control panel’s keypad, relay contacts on the control board close, and complete a circuit from the L1 side to the neutral side of the line.
The control board uses six relays to operate the various functions of the microwave oven (shown below). The relays are controlled by the microcomputer on the control board, and perform the functions shown below.
Relay 4 controls the speed of the blower motor through the control panel. The base thermal fuse will also turn the blower motor on to its low speed if the temperature reaches 133˚F. The schematic configuration for relay 4 is shown in the following diagram. The relay is explained in further detail on the following
page.
L1
(C) |
|
|
|
RELAY 4 |
| BLOWER | (HI) |
(NO) |
| MOTOR | |
|
| ||
(NC) |
|
|
|
| BASE | (LOW) | (C) |
|
| ||
| THERMAL |
| |
|
|
| |
| FUSE |
|
|
Relay 1 | Oven Light/Fan & Turntable Motors |
Relay 2 | High Voltage Section |
Relay 3 | |
Relay 4 (N.C. Contacts) | Auto |
Relay 4 (N.O. Contacts) | |
Relay 5 | Cooktop Lights |
Relay 6 | Night Lights |
|
| MICROCOMPUTER |
CN3 | CONTROL |
|
CIRCUIT | 2 | |
| BOARD | 1 |
|
| |
|
| RELAY RY2 |
|
| RELAY RY4 |
|
| RELAY RY3 |
|
| RELAY RY1 |
| 1 |
|
|
| RELAY RY5 |
|
| RELAY RY6 |
|
|
