21
12.2HPX2400/2800MalfunctionAnalysisonAmplifier:
Sequence
No.
CircuitFunction Failure
1
ClassABPower
Output
‐ Power supply protect: Breakdown of any one power transistor will
causeashortcircuitandresultstohighcurrentprotection.
‐ Amplifier protection: +15 V/‐15Vif the power supply is abnormal
willleadtotheDCoutput,amplifierwillgointoprotectionstatus;
‐
Nocliplimit;
‐ Amplifierself‐excitated.
‐ Cross‐overdistortion;
‐ IC/5532 damaged, unbalanced of the of positive and negative bias
voltage,hasDCoutputandpoweramplifiergoesintoprotection.
2
2HLogicPower
SwitchingCircuit
‐ Lowoutput/earlyClipping:Positiveornegativepowersupplyshould
notbeopened,withoutsecondsteppowersupply.
‐ Theresistanceofamplifiedmoduleisheatingabnormally,positive/
negativepowertransistor(Q19,Q22)isconnectingorshortcircuitfor
longtime;
‐
The abnormal of high‐speed switching comparator / LM311 would
resultstosecondsteppowersupplycouldnotuseandlowoutput.
3 OverloadProtect
‐ Outputshort‐circuitandnoprotect.
‐ Start–upprotect;
‐ Negative‐positivebiasofthepoweroutputtransistorisabnormal;
‐ Smalloutputloadcausedbyfalseoperationofoverload;
4
Short‐circuit
Protection
‐ The protection indicator will not be shined when the amplifier
outputisshort‐circuit.
When signal is increased, the amplifier will go into protection
function.
5 ClipLimit
‐ Nocliplimit;
‐ Cliplimitdelayed;waveformjitterwhenincliplimit;
‐ Volumewillnotgomaximumgraduallyafterstart‐up.
6
VHF/Over‐heat
Protectionand
DelayCircuit
‐ The protection delay circuit is a collection of VHF, short circuit,
over‐temperature,DC‐protection,aswellasstart‐updelay.
‐ Whentheprotectionfunctionandstart‐updelayisabnormalplease
checkthiscircuit.
7 DCProtect
‐ Nooutput‐relaydoesnotpull‐in,firstcheckwhetheritisnormalfor
24Vpowersupply.
‐ On/offhasthesoundofshock‐alongpull‐inontherelay;
Amplifierlongtimeprotection;
RepairingGuide:
1)Whenrepairingtheamplifier,pleaseseriesconnecta100W‐200Wlamptostart‐uptheequipment
toavoidthedamageofrelateddevice;
2)The circuitofCH1and CH2 is thesamebutthesequenceNo. ofdeviceis different,all thetesting
parametercanbeshared;
3)Poweramplifierprotectionmeansthepowerandprotectionindicatorsonthefrontpanelarelit;
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