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Troubleshooting Work Book

Transistor Circuit Troubleshooting  #2

Below we see signal generator providing a 1mv (open circuit) signal at 50 ohms to an amplifier circuit.  The AC voltage verses frequency is plotted for four points: Signal Generator out (Gen Out), transistor Base (B), transistor Collector (C) amplifier output (Ampl. Out). 0 db corresponds to 1 mv. The Base Line curves are for the good unit. You may troubleshoot using the plots for the three faulty unit below and check your answers at bottom of page.

Possible Faults in circuits Below are:
A. 1uf input Capacitor decreased value.
B. 1uf output Capacitor decreased value.
C. 270 ohm resistor open.
D. 4.7k ohm resistor open.
E.  Base (B) to Collector (C) Short.
F. Base(B) to Emitter Short.
G. Collector(C) to Emitter Open

Below we see the response curves of three faulty units. Also shown are four DC levels at the transistor Collector(C), transistor Base(B), circuit input Gen Out, and also at the amplifier output Gen Out

 

 

 

 

Answers Below

 

 

 

 

 

 

 

 

Answer Fault 1

A. 1uf output Capacitior decreased value.

 

 

 

 

 

Answer Fault 2

 

C. 270 ohm resistor is open.

 

 

 

Answer Fault 3

 

F. Base(B) to Emitter Short.

 

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