Fixing a battery charger.

[Tip-C]

damn...are you serious?

Hmmm any ideas on what the specs for that circuit might be?

 

[kchriste]

No. I can't really tell from the pictures you posted. The foil side pic of the entire PCB is good, but there is no corresponding component side photo that shows enough detail for me to figure that out.

 

[Diver300]

I would also say that a better charger with a better way of terminating the charge is a good idea.

If you want to use most of the charger, most standard transformers have only two windings of the same voltage.

For multiple voltages you can either use multiple transformers or voltage multipliers (Jochen's High Voltage Page : Basic multiplier circuits)

Years ago I was given a clock radio that had been fed with about 400 V a.c. and had blown the mains transformer. The LED display ran from 4.5 V, the radio receiver ran from 9V and the clock IC ran from about 12 V and needed the a.c. for the timing. I fitted a 4.5 - 0 - 4.5 transformer, rectified for the LED display, and doubled for the radio. That was the same size as the original transformer and fitted in its place.

For the 12 V, I used a tiny separate transformer. You might be able to fit something like this https://www.electro-tech-online.com/custompdfs/2008/11/0900766b800286a5.pdf as well as a transformer in the same box.

 

[Andrew Leigh]

Hi,

consider this circuit, it was in Elktor (Designed by A. Rietjens). I have built many for friends for various applications and it works like a bomb.

You don't need the selector switch and all the resistors, if you only have one charging rate required then one resistor will simplify the circuit a lot.

Andrew

 

[pfofit]

Since you say the primary has no resistance, then most likely is that most of these transformers have the primary, fused with a thermal fuse called a tco (thermal cut off). Some are rectangular and some are bullet shaped. They blow with temperature and need to be in contact with the windings.

Like these **broken link removed**

Sometimes if your lucky there are just under the outer paper wrap. Put on your surgeon cap and just slice down the paper with a sharp knife. If you see it then measure that, like any fuse it should be a short.

If your unlucky they are buried in the middle of the transfo.

 

[zevon8]

One of the most important bits of information given by the OP in this thread was that the device was "Class 2," This tells that the mains device ( tranformer in this case ) is energy limiting and will open circuit if overloaded, temperature or current.

As noted in the post above, there is a fusing device, most often on the primary of the transformer, sometimes it can be bypassed, other times not. Be aware that bypassing it will remove a safety feature of the design, possibly resulting in a dangerous situation.