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SMPS power supply problem, help
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tedy
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PostPosted: Tue Jun 28, 2005 11:39 am    Post subject: SMPS power supply problem, help Reply with quote

Can anyone plz help me about SMPS power supply. Thus am having trouble to find the problem. It is that I have power in primary, but nothing at secondary. So please tell me more about this. Is it the autocoupler or is it the power transistor , or is it the conroller IC. Plz help me.
tedy
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Al_Dodge_Bundy



Joined: 05 Apr 2005
Posts: 93
Location: Netherlands

PostPosted: Tue Jun 28, 2005 1:14 pm    Post subject: Reply with quote

Very often the small capacitors (e.g. 4.7 uF or 10 uF) on the primairy side of the switched power suply, dry out.
This is due to the heat generated by the primairy power transitor.

Because most of the times, there are only 3 or four small capacitators in the primairy circuit, it is wise just to replace them all.

Many times this helps to "start" the switched power suply again!

Good luck,

Mark
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PostPosted: Tue Jun 28, 2005 2:37 pm    Post subject: Reply with quote

Al_Dodge_Bundy wrote:

Because most of the times, there are only 3 or four small capacitators in the primairy circuit, it is wise just to replace them all.


Capacitators? Are they electrolytic varieties of tubers? Laughing
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absorbentgnome



Joined: 30 May 2005
Posts: 51
Location: Cardiff, UK

PostPosted: Tue Jun 28, 2005 2:39 pm    Post subject: Reply with quote

D'oh! Wasn't logged in.
Mark's has a good suggestion though - and check the chopper transistor for s/c as well and any fusibles around it.
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tedy
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PostPosted: Wed Jun 29, 2005 6:05 pm    Post subject: Reply with quote

What about the autocoupler ( Pc......), the controller IC, Can they stop the power going to the seconday side.
tedy
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Al_Dodge_Bundy



Joined: 05 Apr 2005
Posts: 93
Location: Netherlands

PostPosted: Thu Jun 30, 2005 4:46 am    Post subject: Reply with quote

If you've already replaced the capacitors (better spelling as "capacitators" Very Happy ) and the power supply still isn't starting up, it surely is possible that the controller IC has died.

They are often very cheap, so I would suggest just to replace it and you will know if it's failing!

Grtz Mark

P.s. Also check the resistors that "feed" the control IC, from the 300 V capacitor to the IC. They are most of the times a few 100 KOhms, so you will have to remove them from the circuit to measure their value.
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tedy
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PostPosted: Fri Jul 01, 2005 2:09 pm    Post subject: Reply with quote

thanks. but what about the autocoupler . what is it's function. how can i know if it is faulty. what can be the effects when it is faulty.
tedy
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PostPosted: Fri Jul 01, 2005 8:43 pm    Post subject: SMPS power supply problem, help Reply with quote

http://weber.ucg.ie/mirrors/www.repairfaq.org/sam/smpsfaq.htm#smpstsps
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tedy
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PostPosted: Tue Jul 05, 2005 5:28 am    Post subject: Reply with quote

thanks. but what about the autocoupler . what is it's function. how can i know if it is faulty. what can be the effects when it is faulty.
tedy
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Al_Dodge_Bundy



Joined: 05 Apr 2005
Posts: 93
Location: Netherlands

PostPosted: Tue Jul 05, 2005 11:11 am    Post subject: Reply with quote

Hmm, I'll gues I mixed up the autocoupler and controller IC, my english isn't a 100 %, sorry Laughing

The autocoupler is used to "measure" if there is any secundairy power.
These thing rairly fail. So no need to replace them.

The controller IC can breakdown!, so I meant to replace that one (cause it's usualy cheap)

Grtz Mark
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