N Cook wrote:
:::[...]would a light brown colouring mean it was overcooked
:::and shorted turns a possibility?
:::
When I see orange-brown tape, I think
http://www.google.com/search?q=define:kapton

hr(bob) hofmann wrote:
If it started out yellow and then was turned brown from heat,
I would expect it would not be a uniform brown color.

Yup. *Uniformity* is a big clue.

Tried some yellow tape from a scrapper[...]
Well its certainly not PVC
as it does not melt or shrink at 205 degrees centigrade
but it does go permanently faun brown from the original yellow.

I wouldn't expect to see PVC (electrician's tape?)
over transformer windings.
The yellow tape I've seen is polyester:
more stable than PVC but lower in thermal performance than Kapton.

What I don't understand is that if this colour is due to heat
then why exactly the same shade all around this SMPS transformer,

If I understand the thread, you never saw the original color of the
tape
and think it has changed color to brown, possibly due to a failure.
I'm wondering if Occam's Razor doesn't apply here
(i.e. the original color WAS brown).