Page 66 - Testing Electronic Components

You now have to select your meter to x10Kohm range to test the diode
again. The output voltage of x10k ohms is about 12 Volt (remember the 9
volt battery in your meter-1.5 volt + 1.5 volt + 9 volt = 12 volt). Again
the diode under test should show only one reading. This is exception to
Schottky diode where it has two readings but not shorted reading. I will
explain how to test Schottky diode in the next section.

If the meter showed one reading then the diode under test is good. If it
has two readings then most probably the diode is either shorted or leaky.
The digital meter can't test it because the output from the meter is only
about 500mv to 2 volt.

If a diode breakdown when under full load, there is no way to test the
diode (unless you have a very expensive diode checker or tester which is
specially designed to track this type of fault). Substituting with a known
good diode is often the only way to prove that an intermittent diode is
causing a particular problem. Sometimes an intermittent diode could be
located using a coolant spray and hair blower. Diodes are rated in Voltage
and Ampere. Refer to semiconductor data book for the exact
specification. Always replace a diode with the same or higher rating
than the original specification.

Caution: Be certain that power is removed from any circuit before
performing any of the following diode checks, otherwise meter or circuit
damage could result. Conclusion-In order to correctly testing diode you
need to use analogue multimeter and set the range to x1 ohm and x10
kilo ohms range. With this tips I’m sure you will have the confident to
check any diodes that comes on your way.

66