Thanks for suggestions. The smaller one looks like like it should do the
job with correctly designed converter - the one I found doesn't look like
it can dissipate more than 100mW without damage.
Same story for me and CJ5143 - I've received two of those as free samples.
My converter with CJ5143
Is your transformer (inductor) getting too warm ? It's possible that the
peak current is larger than Isat; at saturation the magnetic efficiency
drops way off.
It's not easy to measure the inductor current, because parasitics are
introduced by the scope-probe. Most often, the ground lead picks-