Question about Samsung SMH7178STD Microwave Oven
Before i jump to the conclusion that you need to check Control Board, i have to think for Defective Electronic Timer.
Symptoms of Defective Electronic Timer are :-
Any type of irregularities or inconsistencies in the display, such as: 1) missing, dimming, flashing, flickering (a slight fluorescent flicker is normal), or overly bright numbers or segments; or 2) the occasional appearance of illogical or mysterious Chinese-like characters (this may also be the result of improper or inadequate grounding).
Any type of programming problems, for example: 1) Pressing one number or function and the panel responding with another; or, some pads program and others do not. These symptoms may be caused by either the touch panel or the control panel or both. 2) Limited or no programming functions. An exception to this symptom is the fact that some models made by Sharp will not program unless the stop switch is in the closed position. Therefore the oven door must be closed and the stop switch properly adjusted before the control panel will accept programming. 3) The control panel "locks up"; maybe one or more numbers will be displayed, but the panel will not reset or program.
The control panel "kicking out" of a cook cycle prematurely, then possibly "locking up." The oven may have to be unplugged then plugged back in before the panel will accept programming. Possible causes: poor or improper grounding; or, excessive amounts of stray RF leakage, either from the latch side of the door, or from the magnetron within the component compartment. If removing the outer case alleviates the symptom, suspect leakage from the RF gasket or the internal structure of the magnetron.
The control panel counts down too quickly or too slowly. Inaccurate timing may also be the result of an oven (of the type that can be converted from 50 to 60 cycles and vice-versa) being set for the wrong voltage or frequency for the area in which it is being used.
The control panel will not start, or fails to count down when started; or, the panel counts down but neglects to activate the cook relay, triac, stirrer or blower motor, or other panel-controlled component. This may also be the result of a misadjusted or defective interlock switch, faulty wiring or related connections, or an open thermal protector or fuse.
NOTE: The triac or triac module (part of many control units) may be checked in several ways.
Either all indicator lights are lit, or no display at all, as though the panel is "dead." (In the case of no display or a "dead" panel, ensure that the low-voltage control transformer is supplying the appropriate voltages. Or if the low-voltage transformer is part of the control board, check for the appropriate input (primary) voltage to the panel before judging it to be defective.)
Either a continuous beep or buzz; or none at all.
The timer buttons remain depressed, thus holding the oven in a continuous cook mode. Litton and some other models use individual pushbuttons that are soldered on to the printed circuit board. These buttons may stick in the depressed position due to inadequate clearance through the cutouts in the timer faceplate. In these cases, the circuit board position may be adjusted to equally center the buttons in their openings, ensuring that the cutouts and buttons are free of grease and residue. In more extreme cases, the size of the hole can be increased by filing the sides of the obstructing cutouts with a small, fine file (the circuit board must be removed first). Then clean any metal filings from the casting and re-assemble the timer, making sure that the timer board is centered so that the buttons operate freely.
Check and let me know.
Hope i helped you.
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Posted on Oct 06, 2009
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Posted on Jan 02, 2017
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