Help finding feedback transformer

[Joun]

Hello
I need help finding this transformer(the small one).It is from the feedback circuit of a 12V 30A power supply.The photo I'm attaching is from another SMPS but It is exactly the same..

Thank you.

[budm]

Re: Help finding feedback transformer

How many widings are there on this little guy?

[Joun]

Re: Help finding feedback transformer

It is T2..

[PeteS in CA]

Re: Help finding feedback transformer

Blech! That is one wretchedly drawn schematic! I've figured out schematics before by looking at PCBs, so I know it isn't easy, but that is not very usable.

Anyway, T2 in that P/S is not feedback. It's the transformer being used to provide base drive to the switch transistors. You would have to unwind it (very carefully!) to figure out what each winding is, and the polarity of the windings. And the details of the construction and the core type are all critical. Winding a new one would not be easy, and mistakes would not be obvious. Mistakes could do damage or be dangerous.

[Joun]

Re: Help finding feedback transformer

It know it is very bad drawn but it is the only one I could find in the net..
Well I'm not going to unwind and wind it back that's for sure.The truth is I took that transformer from a smaller one and solder on this..
I'm saying that I had to ruin a perfectly working 15V 5A in order to fix a 12V 30A.
If there is not any other way I could find the transformer I'll leave it like this..

[budm]

Re: Help finding feedback transformer

M ay I ask on how you figure out that the transformer is bad? It is such too low power to burn up.

[Joun]

Re: Help finding feedback transformer

The whole story goes like this:The power supply come to me with some kind of drink spilled in it(I think sourthen comfort or something like that)
It had a blown fuse and a primary transistor burned,which I replaced and then I washed and dried the PCB.After that it wasn't blowning fuses any more but it didn't work.
I had it open in my bench a few days and every now and then I checked a transistor or a diode ,measuring whatever I could think of but with no luck.
I left at the very end this and primary transformers to check because they rarely go bad(especialy the small one)
To my surprise there was one pin on the primary which was completely open,it didn't had any resistance with any other pin..
Luckily I had a similar power supply(lower wattage and different voltage) which wad inside a identical transformer..I replaced it and it worked like new..
It is a 12V 30A power supply,I tested it at 16A for a few hours and worked just fine..
So I'm saying that it is exactly the same transformer regardless it was used in a different SMPS.

[budm]

Re: Help finding feedback transformer

Since you know that it has open winding, can you try unwrapping the tape to see if you can get access to see the broken wires, you have nothing to loose at this point. I do that on the transformers a lot of time when I have no other choices.