damaged transformer in a TinySwitch SMPS - need help to find a new one - Page 1
Forum section: electronics / projects

author: Chris02
author_rank: Contributor
timestamp: August 06, 2013, 06:35:35 pm
content: 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:1200940100CEC 1033But 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!RegardsChris

author: Experimentonomen
author_rank: Regular Contributor
timestamp: August 06, 2013, 06:40:20 pm
content: 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.

author: ConnorGames
author_rank: Regular Contributor
timestamp: August 09, 2013, 03:38:04 pm
content: 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.

author: c4757p
author_rank: Super Contributor
timestamp: August 09, 2013, 05:01:23 pm
content: It issuchfun! 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

author: SeanB
author_rank: Super Contributor
timestamp: August 09, 2013, 05:26:48 pm
content: 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.

author: Harvs
author_rank: Super Contributor
timestamp: August 10, 2013, 08:18:44 am
content: Quote from: SeanB on August 09, 2013, 05:26:48 pmMost 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.

author: BravoV
author_rank: Super Contributor
timestamp: August 10, 2013, 08:46:20 am
content: Quote from: Harvs on August 10, 2013, 08:18:44 amI assumed the bobbin will be destroyed or badly deformed/melted afterwards ?

author: Harvs
author_rank: Super Contributor
timestamp: August 10, 2013, 09:06:45 am
content: Quote from: BravoV on August 10, 2013, 08:46:20 amNope, 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.