ie the yellow PVC? wrapper often seen around the windings or frame, more so
than mains f transformers.

Is it always yellow?
If light brown with other indications that there was an excessive load and
general overheating, would a light brown colouring mean it was overcooked
and shorted turns a possibility? An original one for this model not seen, so
no idea if it should be light brown or the ubiquitous yellow.

I will try cooking some of the yellow tape stripped from a scrapper.

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/

On Feb 1, 9:00*am, "N Cook" wrote:
ie the yellow PVC? wrapper often seen around the windings or frame, more so
than mains f transformers.

Is it always yellow?
If light brown with other indications that there was an excessive load and
general overheating, would a light brown colouring mean it was overcooked
and shorted turns a possibility? An original one for this model not seen, so
no idea if it should be light brown or the ubiquitous yellow.

I will try cooking some of the yellow tape stripped from a scrapper.

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list onhttp://home..graffiti.net/diverse:graffiti.net/

If it started out yellow and then was turned brown from heat, I would
expect it would not be a uniform brown color.

hr(bob) wrote in message
...
On Feb 1, 9:00 am, "N Cook" wrote:
ie the yellow PVC? wrapper often seen around the windings or frame, more
so
than mains f transformers.

Is it always yellow?
If light brown with other indications that there was an excessive load and
general overheating, would a light brown colouring mean it was overcooked
and shorted turns a possibility? An original one for this model not seen,
so
no idea if it should be light brown or the ubiquitous yellow.

I will try cooking some of the yellow tape stripped from a scrapper.

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list
onhttp://home.graffiti.net/diverse:graffiti.net/

If it started out yellow and then was turned brown from heat, I would
expect it would not be a uniform brown color.

reply

Tried some yellow tape from a scrapper, presumably fairly generic for this
purpose.
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. A
mid shade colour to the example I have here. I will try again but to 220
degrees or so.

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, so it looks like ,
an as-it-came colour. The surrounding core "frame" is also covered with this
tape , not just the windings and its everywhere the same colour, top ,
bottom and sides and winding cover.

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/

Hi!

Is it always yellow?

The vast majority of the ones I have seen are yellow. I suppose this
is the cheapest and therefore most popular color. Most people are
probably never going to look or care all that much. :-)

That said, I have seen some red ones, purple ones and some orange
ones. Something in the back of my mind wants me to say that I've seen
dark brown ones as well, but I'm not sure if that's right.

William

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).

wrote in message
...
Hi!

Is it always yellow?

The vast majority of the ones I have seen are yellow. I suppose this
is the cheapest and therefore most popular color. Most people are
probably never going to look or care all that much. :-)

That said, I have seen some red ones, purple ones and some orange
ones. Something in the back of my mind wants me to say that I've seen
dark brown ones as well, but I'm not sure if that's right.

William

Rummaging around I've just found one with red tape, but dozens of yellow.

I think the small feedback coil at the very centre of this small transformer
has shorted turns. The ps will work with light load if the attenuation in
the feedbak path is reduced, but it all goes outside of operational window
with high load.

Whether the tape was brown or yellow to start with.

Measuring inductance of few random low power such transformers with the main
priomary and fb primary.
One was 1.23mH and 6uH
another
1.47mh and 29uH
this one is
1.16mH and 1uH
looks suspiciously low

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/

In message , N Cook
writes
ie the yellow PVC? wrapper often seen around the windings or frame, more so
than mains f transformers.

Is it always yellow?
No. I've seen green, red and blue as well, I've also seen a Fawn brown
colour and couldn't say if it was always that colour or not.
If light brown with other indications that there was an excessive load and
general overheating, would a light brown colouring mean it was overcooked
and shorted turns a possibility? An original one for this model not seen, so
no idea if it should be light brown or the ubiquitous yellow.
Does the shade change where the tape overlaps? I'd expect a slight
variation, might also be some kind of conformal coating or insulating
lacquer.

I will try cooking some of the yellow tape stripped from a scrapper.

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/






--
Clint Sharp

On Fri, 1 Feb 2008 15:00:14 -0000, "N Cook" wrote:

:ie the yellow PVC? wrapper often seen around the windings or frame, more so
:than mains f transformers.
:
:Is it always yellow?
:If light brown with other indications that there was an excessive load and
:general overheating, would a light brown colouring mean it was overcooked
:and shorted turns a possibility? An original one for this model not seen, so
:no idea if it should be light brown or the ubiquitous yellow.
:
:I will try cooking some of the yellow tape stripped from a scrapper.


The Yellow tape is most likely 1 mil polyester film

eg. Permacel P256 or similar http://www.permacel.com/pdfs/P-256%20YLW.pdf

If you care to search through the Permacel products gallery you will see that
other there are other color adhesive tapes for the electrical and electronic
industries http://www.permacel.com/

Ross Herbert wrote in message
...
On Fri, 1 Feb 2008 15:00:14 -0000, "N Cook" wrote:

:ie the yellow PVC? wrapper often seen around the windings or frame, more
so
:than mains f transformers.
:
:Is it always yellow?
:If light brown with other indications that there was an excessive load
and
:general overheating, would a light brown colouring mean it was overcooked
:and shorted turns a possibility? An original one for this model not seen,
so
:no idea if it should be light brown or the ubiquitous yellow.
:
:I will try cooking some of the yellow tape stripped from a scrapper.


The Yellow tape is most likely 1 mil polyester film

eg. Permacel P256 or similar http://www.permacel.com/pdfs/P-256%20YLW.pdf

If you care to search through the Permacel products gallery you will see
that
other there are other color adhesive tapes for the electrical and
electronic
industries http://www.permacel.com/

I don't know what the 130 deg C refers to, but this tape and adhesive holds
up well to short duration temp of 205 deg C , by 240 deg C it is puckering
and losing conformity and adhesion - pretty impressive really for non ptfe
tape.

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/