Transcript Troubleshooting of PA system

TROUBLESHOOTING OF PA SYSTEM
Submitted by
RAVI JAGANI
NEERAJ KUMAR
130280111096
130280111127
CONTENT

Introduction

Block diagram of PA system

Flowchart for troubleshooting in PA system

Symptom, likely fault and its remedy
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 .
BLOCK DIAGRAM OF PA SYSTEM
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 ).

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.

FLOWCHART FOR TROUBLESHOOTING IN PA SYSTEM
SYMPTOM, LIKELY FAULT AND ITS
REMEDY
Fault
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.
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Remedy


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).
SYMPTOM, LIKELY FAULT AND ITS
REMEDY
Fault


The presence of noise
shows that the preamplifier 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.
Remedy
Check by meter and
rectify the fault.
 Check the divergent
circuits by isolation
method, and located
and remove the fault.

SYMPTOM, LIKELY FAULT AND ITS
REMEDY
Fault
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.
SYMPTOM, LIKELY FAULT AND ITS
REMEDY
Fault

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.
Remedy

Check the source of
distortion by shortcircuiting 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
THANK YOU