Page 64 - Testing Electronic Components

To be absolutely sure, you will need to lift, or disconnect, one diode lead
from the circuit to avoid back circuits. Unless you are very sure about the
board you are checking. Sometimes I do found bad diodes when checking
it on board. Your experienced will tell you when to test a diode on-board
or off-board. If you are a beginner, I highly suggest that you measure
a diode with a lead removed from the board to avoid any confusion
results from your meter.

If you reverse the probes the pointer will not move at all

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