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11.2MalfunctionAnalysisonSMPS:
Sequence
No.
CircuitFunction Failure
1
Line
Filter/Soft‐start/
Rectification
‐ The AC fuse of the rear panel is burnt when connected the
electricity‐checktheRT1deviceandlinefilterdevicetoseeifthereis
shortcircuit.
‐ There is smoke but it can still work while output power, check
whetherthethermistor/ NPTR1
wasburntcausedbytherelaydidn’t
pull‐in;
‐ Connect the jumper of 110V and ACI port,the double voltage
rectifierwillletthecircuitworkin110Vand120Vstatus;
2
LLCResonant
Converter
‐ 85°C thermal switch is often closed result to the start‐up
unavailable;
‐ Whilestart‐uptheequipment,high‐currentwillresultstotheburnt
outoftheprimaryDC/DC/300Vfuse;
‐ Switching transistor is not working, check the driving transformer
T2, a loop is formed
by the primary current go through the
transformerT1A,resonantinductorL4andresonantcapacitorC106;
3
FanSpeed
ControlCircuit
‐ Fansdonotwork.
‐ Fastrotating.
‐ Itiseasilytogointoover‐heatprotectionifthefansdon’tspeedup
afterthemoduletemperatureincreasing.
4 RectifierOutput
‐ Powerprotectioncausedbythe damageof high‐speeddiodesD49,
D50,D51,D52,D67,D68, D73,D74,E4,E5,E7,E8,C6,C7,C8, C9, or
anyofrectifierfilterdevice.
‐ Poweramplifierstart‐upprotection.
‐ Outputdistortionandpowerprotectioncausedbyno
±15Voutput;
‐ All the indicators on the panel do not shined because no +24V
output(start‐upunavailable).
RepairingGuide:
1) When repairing the power board, please cut the DC/300V fuse, series connect a 100W—200W
lamptostartthemachine,preventingthedamageofrelateddevicewhenrepairing.
2) When the SMPS can not be started, repeats the protection and restart, please disconnect +VCC,
‐VCC then try to
start, if it is normal, it means short‐circuit in amplified part, check the amplified
circuit,otherwiseitisthefailureofSMPS;
3) Power supply protection means‐all the indicators on the front panel lit and then immediately
blackout;
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