[SOLVED] SMPS output flickering

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ismu

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in my Tecktronics TDS100c model internal SMPS is from Emerson , it has been damaged , its TOP244yn IC is gone bad[smoke is there near] , so i replaced with new one , after that out put is coming 3.3v but it will on at 2sec and off at 2sec and repeating ,i didnt check other sections may same issue ., what should i change .see the picture ..
 

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i think there is a problem with current sense section
 
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    ismu

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can suggest where is the current sense laction in top244yn ic or any related components ?
 

check the optoisolator and high watt resistors or replace th optoisolator if you have.
 
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    ismu

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where will be the high wattage res? which one?can u check below picture , i think opto is 817
 

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can you post the backside of the pcb?
 
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    ismu

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Hi,

have you cleaned the smoked part of the PCB properly? There might be slightly conductive residuals.
Or an old electrolytic capacitor,
or a lot of other reasons.


Klaus
 
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    ismu

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yes , i cleaned well

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in top244yn data sheet they mensioned reference design , can u refer that schematic and wich may be the resistor whch u have mensioed earlier? currently body is not with me ./
 

i suggest you to check all the resistors carefully (specially high watt resistors like R7,R8,R5 etc) and the diodes specially D6,D7 with multimeter
 
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    ismu

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H all friends

i got the issue and now it is working fine , the problem was optocoupler has been damaged , i replaced it.

Thanks all [specially hamid159 ] for your valuable replay .

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glad....your problem has solved.
 
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    ismu

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