On 27 Aug 2005 17:12:01 -0700, "
wrote:

Generic ctc177 power supply schematic available at
alt.binaries.schematics.electronic


This type of SMPS based on STK730-xxx uses one winding on this
transformer (hot side only) for regulation feedback.

The STK730 is triggering on bogus feedback (weak voltage) that makes
output rocket to the moon. Change 10uF 63V cap, and very, very
carefully check the feedback circuit for loss of feedback strength.

When you say isolated ground in reference to measuring items, I assume
cold side, hence the confusion for all of us including you. Measure
always in same side hot ground for hot or cold ground for cold. Not
across, this will gave you bogus readings. This is reason to use
isolation transformer while messing in any chassis that has no
insulated & isolated power. SMPS and hot chassis (like CTC185) is not
isolated bec the hot side is still exposed.

Cheers, Wizard