Here you will find diode tests and scr tests
The meter gives three different readings depending on how you
connect the diode, forward or reverse, and what setting you
have the meter set to: "ohms" or "diode test".
From left to right:
Test 1 is done with meter on 'ohms' and diode connected in the
forward direction. This test should read fairly low ohms on the
meter. This means anything from maybe 100 ohms to 100k depending on
the meter. If you read zero ohms or extremely low ohms (under 1 ohm)
then most likely the diode is shorted. If you read very high ohms then
the diode might be open, but there is a chance your meter cant bias the
diode correctly so make sure you perform test 3 below.
Proceed to test 2.
Test 2 is done with the meter on 'ohms' and diode connected in
reverse as shown by the center diagram above. The meter should read
very high ohms, typically 500M (that's 500megohms). If your meter
doesnt go up that high, then you should at least see the meter go
off scale so as to make the diode look 'open'.
Test 3 is done with meter on 'diode' and diode connected in the
forward direction as shown in the diagram to the far right above.
This test usually shows the forward voltage of the diode with a small
bias current applied by the meter. You should typically see between
about 0.4 to 0.9 volts for standard silicon diodes. If you see under
0.1 volt the diode might be shorted, and if you see over 1 volt it
may be open.
You can also bias the diode yourself with a small battery and a resistor
and check the forward voltage with the meter set to DC volts.
To do this, wire a 10k resistor in series with a 9v battery and connect
the diode in the forward direction. Then, measure the voltage across
the diode and look for something between 0.4 and 0.9 volts.
If any of the above tests fail you might want to replace the diode
with a new one that checks out good.
Wall Wart Internal Resistance Test
Cell Capacity Test Jig
200ma discharge test