damaged transformer in a TinySwitch SMPS - need help to find a new one

[Chris02]

Hi!

It is my first post in this forum and I hope I'm in the right section.

My Name is Chris, 26 from Germany and studying electronic engineering.

My 3 years old tryer stopped working. Nothing happens anymore. I checked the power electronics and saw a burned resistor. This resistor connects the secondary VCC to earth (not to ground). Between the resistor and the connectionpad for the earth cable is a track loop. I can't read the value of this resisto and don't know why it is connected to earth. Maybe someone knows it?

I attached a picture of this PCB part.

The transformer is burned at the secondary site too. The transformer is marked with:

1200940100
CEC     1033

But I can't find anything with this codes.

But I guess it will be possible to identify the trnsformer by checking the circuit.

The SMPS is built with a Power Integrations TinySwitch (TNY254).

After the TNY254 is a one wave rectifier and a 16V cap to filter the voltage. This voltage is VCC of the secondary side now.

I know that it must be between 1,8V and 5,5V because it is also VCC for a microcontroller (Nec PD78F9177).

I hope you can help me to find a new transformer and repair my dryer!

Thanks!

Regards
Chris

[Experimentonomen]

These transformers are not off the shelf items, they are custom made so your not gonna find a replacement transformer.

Your gonna have to find/buy a replacement board.

[ConnorGames]

Or if you REALLY want to have fun, you could try to rewind the transformer. I have never done that before, but I have heard that it is not exactly fun.

[c4757p]

It is such fun! Yesterday my stash of magnet wire ran out, so I had to paint my entire house with a toothpick instead. Still wasn't quite as fun as rewinding transformers, though

[SeanB]

Depends on the transformer. Some are very easy to rewind, some are a royal PITA to do. If it has been glued together during assembly with varnish or even worse potted I generally get a new core and bobbin, then do a destructive disassembly of the old one to get the counts and construction.

Fun is rewinding motor armatures.

Even more fun is rewinding syncro resolvers with 60 SWG wire and a magnifier. Especially as you need to get those 600 turns into the space they were in originally by hand winding them through the slot.

[Harvs]

Depends on the transformer. Some are very easy to rewind, some are a royal PITA to do. If it has been glued together during assembly with varnish

Most glued transformer cores can be separated with heat.  Sometimes a hot air gun is all that's needed, other times I've use a small torch right on the joints.

[BravoV]

Most glued transformer cores can be separated with heat.  Sometimes a hot air gun is all that's needed, other times I've use a small torch right on the joints.

I assumed the bobbin will be destroyed or badly deformed/melted afterwards ?

[Harvs]

Most glued transformer cores can be separated with heat.  Sometimes a hot air gun is all that's needed, other times I've use a small torch right on the joints.

I assumed the bobbin will be destroyed or badly deformed/melted afterwards ?

Nope, just direct the air or flame at the core joint (assuming an E core) and they come apart pretty quick.  I've never damaged a bobbin before doing this.  I've often grabbed the main flyback transformers out of CRT monitors and reused them.