Elenco Upgrade Kit SC500 to SC750 - Manual (Page 27)

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Project #553
OBJECTIVE: To test your NPN transistor.
Solar NPN Transistor
Tester
This circuit is just like the one in project #551, but tests the NPN
transistor (Q2). The meter will read zero unless both switches (S1 &
S2) are on, then the adjustable resistor (RV) sets the current. If you
have the same light and RV setting as project #552 with the diode
(D3), then the meter (M2) reading will be higher with the transistor.
You can replace the NPN transistor with the SCR (Q3), it works the
same way in this circuit.
Project #554
OBJECTIVE: To test your PNP transistor.
Solar PNP Transistor
Tester
This circuit is just like the one in project #551, but tests the PNP
transistor (Q1). The meter (M2) will read zero unless both switches
(S1 & S2) are on, then the adjustable resistor (RV) sets the current. If
you have the same light and RV setting as project #552 with the diode
(D3), then the meter reading will be higher with the transistor.