1. Troubleshooting of PA system
Submitted by
RAVI JAGANI
NEERAJ KUMAR

2. CONTENT Introduction Block diagram of PA system
Flowchart for troubleshooting in PA system
Symptom, likely fault and its remedy

3. INTRODUCTION
Troubleshooting means to locate the faulty component or connection in the equipment and determining the cause of its becoming faulty.
Maintenance includes corrective maintenance (repair), qualitative maintenance (restoring specifications) and preventive maintenance (servicing), audio and video equipment which use PCBs , diodes, transistors, ICs, etc.
Need careful handling not only in operation, but also in fault-diagnosis and repair .

4. BLOCK DIAGRAM OF PA SYSTEM

5. BLOCK DIAGRAM OF PA SYSTEM
Microphone :- Its pic up a sound wave and convert them into electrical variation, called sound signal.
Mixer:- It is for effectively isolate different channels from each other before feeding to the main amplifier.
Voltage amplifier:- Its amplifies the output of the mixer.
Processing circuit:- This circuit have master gain control and tone control (bass and treble control ).

6. BLOCK DIAGRAM OF PA SYSTEM
Driver amplifier:- It gives voltage amplification to such extent that internal resistance of that stage is reduced. thus, it drives the power amplifier to give more power.
Power amplifier:- It gives the desire power amplification to the signal.
Loudspeaker:- It converts electrical audio signal into pressure variation resulting in sound.

7. Flowchart for troubleshooting in PA system

8. Symptom, likely fault and its remedy
Set is not getting power supply. Fuse might have blown off, or mains lead/plug disconnected or power supply unit defective.
Loudspeaker leads might have become short-circuited or broken or LS coil short.
Check the mains line and power- supply unit to locate the fault. Rectify the fault.
Check the short by resistance measurement (remember16/02 feeder gives 6 ohm per 100m), and check the feeder by capacitance measurement (typical capacitance of feeder is 30pF per meter).

9. Symptom, likely fault and its remedy
The presence of noise shows that the pre- amplifier and other stages are alright. Hence microphone lead open or shorted to shield.
Short circuit in the power supply unit, or some stage short circuiting the power supply line.
Check by meter and rectify the fault.
Check the divergent circuits by isolation method, and located and remove the fault.

10. Symptom, likely fault and its remedy
Speaker defective, or the fault is in loudspeaker lead, or connector
Emitter bypass capacitor open.
Check the loudspeaker circuit by resistance measurement and remove the fault.
Measure gain of stages by split half method and thus identify the faulty stage. Replace the faulty component.

11. Symptom, likely fault and its remedy
Positive feedback causing high pitched whistle. Sometimes the output may be supersonic. Such supersonic oscillations will not be heard but they will over load the amplifier and cause distortion.
Check the source of distortion by short- circuiting input of stages one by one and thus identify the defective stage or undesired coupling and rectify it . Check the negative feedback component and replace the faulty component

12. Thank you