11
6.2MalfunctionAnalysisonAmplifiedPart
Sequence
No.
CircuitFunction Failure
1
ClassABPower
Output
‐ Powersupplyprotection:Anyoftheshortcircuitsofpoweroutput
transistor(CH1/Q2,Q3,Q10,Q11,CH2/Q19,Q20,Q24,Q25)willcause
thehighcurrentandpowersupply protection;
‐ Amplifierprotection:+15V/‐15Visderivedfromthecurrentlimiting
ofR31,R40and
D3,D4,ifthepowersupplyisabnormalitwillleadto
theDCoutput,amplifierwillgointoprotectstatus;
‐ Cliplimitdoesn’twork–checkwhetherthedevicesofD7,D8,D9,
D40,LED1,R22isdamagedornot;
‐ Amplifierself‐excitation–checkwhetherthe
deviceofC3,C7,C8,
C10,C14wasturnbad.
‐ Crossoverdistortion:checkwhethertheBEvoltageofthe
negative‐positivehalf‐wavepowertransistoris<0.2Vornot,thencheck
thevalueoftemperaturecompensationtransistorQandresistance
(R25,R26,R13)ischanged;
‐ IC/5532damaged,unbalanced
oftheofpositiveandnegativebias
voltage,hasDCoutputandpoweramplifiergoesintoprotection.
2
Overload/
Short‐circuit
Protection
‐ Outputshort‐circuitandnoprotection,
‐ Start–upprotection
3
ClipLimit
Circuit
‐ Nocliplimit,checkwhethertheD7ison;
‐ Cliplimitdelayed,checktheD9andR19;
‐ Waveformjitterwhenincliplimit;
‐ Novolumegraduallyincreasefunctionafterstart‐up.
4
Over‐temperature
Protectionand
DelayCircuit
‐ The delay circuit protect is a collection of VHF, short circuit,
over‐temperature,DC‐protection,aswellasstart‐updelay.
‐ When the Protection function and start‐up delay is abnormal please
checkthiscircuit.
5 DCProtectCircuit
‐ Nooutput‐relaydoesnotpull‐in,firstcheckwhetheritisnormalfor
24Vpowersupply,Q6baseisahighlevel.
‐ On/offhasthesoundofshock‐alongpull‐inontherelay;
RepairingGuide:
1)Whenrepairingtheamplifier,pleaseseriesconnecta100W—200Wlamptostarttheequipmentin
ordertoavoidthedamageofrelateddevice;
2)ThecircuitofCH1andCH2isthesamebutthesequenceNo.ofdeviceisdifferent,allthetesting
parametercanbeshared;
3)Poweramplifierprotectionmeansthepowersupplyandprotectionindicatoronthepanelarelit;
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