Help with ICL power supply fault (Farnell SMPS)

Tony Duell ard at
Thu Apr 10 16:32:20 CDT 2008

> Hi,
> I've started to setch the output circuitry, not 100% accutarely as my 
> meter shows all the transformer windings as 0 ohm, so I have some points 
> that measure 0 ohm to ground which may be ground or maybe a transformer 
> output. 

Thsi is not surpising. the secondary windings of most SMPSU transformers 
are perhaps 10 turns of thick wire. 

When I've traced out scheamtics of SMPSUs (and for that matter monitors, 
which also have low-resistance coils/transformers in them) I've had to 
desolder all 'wound' components from the PCB. It's not too bad if said 
components have the connections brought out to pins which are soldered to 
the PCB, you can remove the component in one go, and have no problems 
getting it back correctly. But some PMPSUs have chopper transformers with 
flying leads for some of the secondary winding connections. THose have to 
be desoldered, and a note made of how to get them back.

Be warned that an inaccurate circuit diagram will drive you mad.


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