Troubleshooting of SMPS
Troubleshooting of SMPS
1. Symptom - Nil depletion at input socket.
Solution - Check only series component (Fuse, R.F Coil, N.T.C and On/Off
Switch).
2. Symptom - Beep sound available at input impedance (Live and Neutral)
Solution – Check only parallel component (Distortion capacitor, Bridge diode,
M.F.C, Start up Transistor).
First of all disconnect start up transistor and check condition if problem
solve mains start up transistor faulty bur same problem again disconnect N.T.C
and check condition If same problem mains distortion capacitor faulty or nil
depletion mains bridge diode or M.F.C any one faulty.
3. Symptom - Start up transistor and switching transistor Impedance.
Solution – M.M beep range red probe put at flouting ground negative of M.F.C
and black probe put at transistor terminal.
4. Symptom - Check OSE I.C Impedance.
Solution – M.M beep range red probe put at main ground black probe put at I. C
pin one by one.
Note – If nil depletion available at any pin mains open type faulty.
5. Output Impedance – M.M beep range red probe put at main ground and black probe
at all out put voltage track or wire.
6. Symptom - Nil voltage at start up Tr. Collector terminal.
Solution – Check 300v D.C at M.F.C. if voltage available mains line filter circuits
ok other wise check line filter circuit only series components. If required voltage at
M.F.C and nil voltage at collector mains low value fusible resistor is open.
7. Symptom - Nil voltage at base of start up Transistor.
Solution – Check kicking resistor may be open or dry soldering.
8. Symptom - More voltage available at base terminal of start up transistor –
Solution – check feedback component (resistor, capacitor, and diode) may be
open or dry soldering.
9. Symptom - Mother board censing circuit faulty Pin No. 14 of power connector nil
voltage –
Solution – Check constant +5v at Pin 13, 14, 15 of oscillator I.C if ok voltage
available mains only high value resistor opens.
10. Symptom - If start up circuit and mother board censing circuit both is ok and after
grounding pin
No. 14, nil voltage -
Solution – Check divider capacitor may be open and dry soldering if capacitor ok
check switching transistor Q1 and Q2, PWMC, low value resistor and PDR attach with
base to emitter may be open and dry soldering.
11. Symptom - Less voltage out from SMPS –
Solution – If less voltage available in proper racio mains output rectifier and
filter circuit are ok. Such as – Shout key diode, power diode, main chick coil, output filter
coil and output filter capacitor, then ground Pin No. 4 of power OSC I.C and again
check output voltage after ground Pin 4 require voltage available at all output track
mains oscillator I.C ok, check Pin No. 1, 2, 6 and 5 pin components.
Note – Multi Miter adjust 20v D.C range black probe main ground red probe at output
voltage track.
1. Symptom - Nil depletion at input socket.
Solution - Check only series component (Fuse, R.F Coil, N.T.C and On/Off
Switch).
2. Symptom - Beep sound available at input impedance (Live and Neutral)
Solution – Check only parallel component (Distortion capacitor, Bridge diode,
M.F.C, Start up Transistor).
First of all disconnect start up transistor and check condition if problem
solve mains start up transistor faulty bur same problem again disconnect N.T.C
and check condition If same problem mains distortion capacitor faulty or nil
depletion mains bridge diode or M.F.C any one faulty.
3. Symptom - Start up transistor and switching transistor Impedance.
Solution – M.M beep range red probe put at flouting ground negative of M.F.C
and black probe put at transistor terminal.
4. Symptom - Check OSE I.C Impedance.
Solution – M.M beep range red probe put at main ground black probe put at I. C
pin one by one.
Note – If nil depletion available at any pin mains open type faulty.
5. Output Impedance – M.M beep range red probe put at main ground and black probe
at all out put voltage track or wire.
6. Symptom - Nil voltage at start up Tr. Collector terminal.
Solution – Check 300v D.C at M.F.C. if voltage available mains line filter circuits
ok other wise check line filter circuit only series components. If required voltage at
M.F.C and nil voltage at collector mains low value fusible resistor is open.
7. Symptom - Nil voltage at base of start up Transistor.
Solution – Check kicking resistor may be open or dry soldering.
8. Symptom - More voltage available at base terminal of start up transistor –
Solution – check feedback component (resistor, capacitor, and diode) may be
open or dry soldering.
9. Symptom - Mother board censing circuit faulty Pin No. 14 of power connector nil
voltage –
Solution – Check constant +5v at Pin 13, 14, 15 of oscillator I.C if ok voltage
available mains only high value resistor opens.
10. Symptom - If start up circuit and mother board censing circuit both is ok and after
grounding pin
No. 14, nil voltage -
Solution – Check divider capacitor may be open and dry soldering if capacitor ok
check switching transistor Q1 and Q2, PWMC, low value resistor and PDR attach with
base to emitter may be open and dry soldering.
11. Symptom - Less voltage out from SMPS –
Solution – If less voltage available in proper racio mains output rectifier and
filter circuit are ok. Such as – Shout key diode, power diode, main chick coil, output filter
coil and output filter capacitor, then ground Pin No. 4 of power OSC I.C and again
check output voltage after ground Pin 4 require voltage available at all output track
mains oscillator I.C ok, check Pin No. 1, 2, 6 and 5 pin components.
Note – Multi Miter adjust 20v D.C range black probe main ground red probe at output
voltage track.
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