Control / Oscillator Section in SMPS
Control / Oscillator Section in SMPS
Identification: In this section has Control IC Tl 494/KA 7500, Driver transformer S.Winding.
Function: Control section is ON the SMPS and Constant the output Voltage.
Isolation: If Out put is proper , is means this section is ok . and after short Green and Black SMPS is ON and output Voltage also proper , It Means this section is ok. otherwise Faulty.
NOTE: BUT PRESENT SMPS HAS ONE IN , IT CONTROL TWO SECTION LIKE CONTROL AND PG SECTION.
Problem and Solution
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.
Symptom - If start up circuit and mother board sensing 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.
Symptom - Less voltage out from SMPS –
Solution – If less voltage available in proper mains output rectifier and
filter circuit are ok. Such as – schottky diode, power diode, main 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.
Identification: In this section has Control IC Tl 494/KA 7500, Driver transformer S.Winding.
Function: Control section is ON the SMPS and Constant the output Voltage.
Isolation: If Out put is proper , is means this section is ok . and after short Green and Black SMPS is ON and output Voltage also proper , It Means this section is ok. otherwise Faulty.
NOTE: BUT PRESENT SMPS HAS ONE IN , IT CONTROL TWO SECTION LIKE CONTROL AND PG SECTION.
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| Control Section using TL494 /KA7500 |
Problem and Solution
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.
Symptom - If start up circuit and mother board sensing 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.
Symptom - Less voltage out from SMPS –
Solution – If less voltage available in proper mains output rectifier and
filter circuit are ok. Such as – schottky diode, power diode, main 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.
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