Diode. How to test a diode by multimeter on-board and off-board, that is, to learn working or not, and to determine which of the conclusions of an anode and a cathode? To do this, use the function continuity test, which is present in any multimeter.
The diode has the property of unidirectional conductivity, i. e. Only conduct current in one direction and not in the opposite holds. The conducting direction of the diode is low resistance, and high in the non-conducting. Therefore, if the diode to apply a direct voltage to the anode i.e., plus and minus the cathode, then it will open and will flow through current. If the diode to apply a reverse voltage - minus the anode and the cathode plus, it is closed and current will not flow through it.
Now take a multimeter and set it to "continuity test" mode circuit. Connect the test probes to the diode terminals and fix the meter readings, then switch places and prikosnёmsya probes to opposite conclusions. The diode is serviceable, if in one case it is conducting, and the second does not hold. If the meter readings are identical in both cases, that is, the diode conducts current in both directions, or does not make any one, it is defective. The most common neiskpavnostyu diode is a breakdown. In this case, it conducts current in both directions. This diode must be replaced. Very rarely there are cases when the diode does not conduct current in both directions.
How to check a diode on the board? To obtain reliable information necessary to unsolder one of the diode terminals.
Determining serviceability clearly shown in the diode D226, D9 and 1N4007.

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