Manual

-149-
T
ransistors are very important, and you may need to
test them to be sure they are working. You can’t tell
if one is working just by looking at it, but this circuit
l
ets you test them. This circuit also checks whether a
transistor is a PNP or an NPN.
You’ll notice that this project has three long wires -
one for the emitter, one for the collector and one for
the base. The schematic shows the terminals
marked for checking PNP transistors.
To use this experiment, connect the long wires to the
base, collector, and emitter of the transistor you want
to test. Turn the control fully counter-clockwise.
Then, press the key and turn the control clockwise.
The transistor is a working PNP transistor if you hear
a sound from the speaker. If you hear no sound at all,
change connections 4-124 and 119-138 to 4-119 and
124-138, and repeat the test. If you get a sound from
the speaker this time, the transistor is a working NPN
type. If you get no sound from the speaker using
either set of connections, the transistor is defective.
You’ll find this a handy circuit for testing unmarked
transistors as you start to accumulate parts for other
electronic circuits.
N
otes:
EXPERIMENT #127: TRANSISTOR TESTER
Schematic
Wi
r
i
ng Seque
nce:
o
1-
29
o
2
-
30
o
3-
10
5-
COLLECT
OR
o
4-
124
o
5-
94-
1
06-
11
0
o
26-
72
-
137
o
27-
71
o
28-
EMI
TTER
o
93-
109-
BASE
o
119-
13
8
o
121-
12
2
EP-130_62315RevC.qxp_EP-130_062812 6/23/15 11:18 AM Page 149