10 Apr
2008
10 Apr
'08
2:32 p.m.
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.
-tony