Sanyo SM-GA0005 service manual Typical Circuit Analyasis of Microwave Oven, Schematic Diagram

8). It is the most liable place where microwave leakage occurs. Especially, after a long time using, the microwave leakage would enlarge at the hinge and the hook. Anyway, mechanic damage would also cause large amount of microwave leakage. Therefore, the main methods designed for preventing microwave leakage of the door are as follows:

1)Assemble a layer of steel filament or a thin metal plate with many holes at the middle of the window to made it is possible to observe the heating as well as shielding the microwave.

2)The widely used seal measurement at present is to assemble a current – resistant construct between the door and the doorframe. FIG.2-9 is the typical construction fig of the door. It was designed according to the theory of

“THETRANSFERING LINE ONE–FOURTHWAVE LENGTH IMPEDANCE CHANGER”. Although there is no connecting point from a mechanical point. It is sealed at the seam from the point of electricity, so it is called “CURRENT-RESISTANT”. Recently, with the installation of noise filter in the current resistant trough, the effect to restrain the microwave leakage (include high subharmonic) have been much improved.

current-resistant constructure

front door plate

noise filter

oven door

Fig.2-9

3. TYPICAL CIRCUIT ANALYASIS OF MICROWAVE OVEN

We have introduced the structure and the working principle of the microwave oven previously. We shall analyze the complete set circuit of the microwave oven link with the practical circuit at this chapter.

		SCHEMATIC	DIAGRAM
		NOTE: Door is closed				MAGNETRON
		Unit is not operated
						FA
						F
			PRIMARY		POWER	C
FUSE			SWITCH		RELAY
L						HIGH
						VOLTAGE
	MONITOR				TURN-	CAPACITOR
120V
	SWITCH	OVEN	FAN		TABLE
60Hz
		LAMP	MOTOR		MOTOR	HIGH
		L	FM	MT		VOLTAGE
THERMAL						DIODE
CUTOUT
(MAG.)	(OVEN)	MAIN
N
		RELAY
SECONDARY						HIGH
SWITCH						VOLTAGE
						TRANSFORMER

DIGITAL PROGRAMMER CIRCUIT

LOW VOLTAGE

TRANSFORMER

10