Hello, Im looking for help identifying what I need to repair a power supply that has stopped working. The supply is a 240V AC to 21.6V 1A DC (seems really random) and is an outdoor power supply. I have opened up the supply, taken off all the silicone that was in there waterproofing and immediately there was charring and the notorious dead electronics smell coming from the transformer. I have de-soldered it ( there are 4 legs on the input HV side and 3 legs on the output LV side.) I have un-would it and from the looks the very bottom winding has shorted and felt slightly wet so I am guessing it failed from water ingress. Anyway after a few hours of searching online I cant for the life of me find a similar looking transformer to replace it with. If anyone can help I would greatly appreciate it. Thanks

 

Pictures

 

There is Hammond Transformers have a fairly wide range, the alternative is to pick up a toroidal type that is close, they are easy to add or subtract windings if needed.
I just saw the photo's and it appears to be a SMPS supply. So that makes it a little different.
Do you need regulation? As a linear supply is much hardier and easier to fix.
Max.

 

There is Hammond Transformers have a fairly wide range, the alternative is to pick up a toroidal type that is close, they are easy to add or subtract windings if needed.
I just saw the photo's and it appears to be a SMPS supply. So that makes it a little different.
Do you need regulation? As a linear supply is much hardier and easier to fix.
Max.

Uploaded a picture of the full board. It's a charger for a Lithium ion robotic lawnmower which they want £93 to replace. The mower its self has over current protection and the charging circuit in there so I wouldn't think the power supply needed regulation too. I've just ordered a cheap 24v power supply which has a +/- 10% adjustment pot. And it just so happens -10% is 21.6V so maybe that's what I need. But I still intend to fix this out of principle!

I'll definitely go have a look at those thanks for the help. Another bit of info is that there were 5 separate layers of windings (I was expecting just 2). It's only the inner most winding that is charred so I'm almost tempted to try rewinding and see what happens.

 

You could look for an existing wall wart that is close in voltage, I imagine it doesn't have to be potted either?
In some cases I have removed the case from the W.W. and included it on a PCCT board.
Max.

 

if your new psu can be adjusted, then it can be modified to give 26v out easily.

as for the old psu, forget it, the transformer has blown up because the mosfet has blown too.

 

if your new psu can be adjusted, then it can be modified to give 26v out easily.

as for the old psu, forget it, the transformer has blown up because the mosfet has blown too.

I'd hope it was just a case of water ingress, but yea I've read that the capacitors and trim sisters would need to be replaced if doing the job fully. I guess I'll get a waterproof housing for the new supply and experiment.

You could look for an existing wall wart that is close in voltage, I imagine it doesn't have to be potted either?
In some cases I have removed the case from the W.W. and included it on a PCCT board.
Max.

I had thought about just getting a 21V laptop supply and under-volting a bit but the 24V supply was cheaper so I'll give that a spin.